[svn-r23913] some refactoring of the server side access to IOD

9 files changed, 787 insertions, 688 deletions

diff --git a/src/H5VLiod_attr.c b/src/H5VLiod_attr.c
index 8565882..dd8c786 100644
--- a/src/H5VLiod_attr.c
+++ b/src/H5VLiod_attr.c
@@ -47,19 +47,17 @@ H5VL_iod_server_attr_create_cb(AXE_engine_t UNUSED axe_engine,
     op_data_t *op_data = (op_data_t *)_op_data;
     attr_create_in_t *input = (attr_create_in_t *)op_data->input;
     attr_create_out_t output;
-    iod_handle_t coh = input->coh;
-    iod_handle_t loc_handle = input->loc_oh;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t loc_handle = input->loc_oh; /* location handle to start lookup */
     iod_obj_id_t loc_id = input->loc_id; /* The ID of the current location object */
     iod_obj_id_t attr_id = input->attr_id; /* The ID of the attribute that needs to be created */
-    iod_handle_t attr_oh, attr_kv_oh, cur_oh, mdkv_oh;
+    iod_handle_t attr_oh, attr_kv_oh, cur_oh, mdkv_oh; /* object handles */
     iod_obj_id_t cur_id, mdkv_id;
-    const char *loc_name = input->path;
-    const char *attr_name = input->attr_name;
-    char *last_comp = NULL;
-    iod_array_struct_t array;
-    iod_size_t *max_dims;
-    iod_kv_t kv;
-    size_t buf_size;
+    const char *loc_name = input->path; /* path to start hierarchy traversal */
+    const char *attr_name = input->attr_name; /* attribute's name */
+    char *last_comp = NULL; /* the last component's name where attribute is created */
+    iod_array_struct_t array; /* IOD array structure for attribute's creation */
+    iod_size_t *max_dims; /* MAX dims for IOD */
     scratch_pad_t sp;
     iod_ret_t ret;
     hbool_t collective = FALSE; /* MSC - change when we allow for collective */
@@ -121,45 +119,26 @@ H5VL_iod_server_attr_create_cb(AXE_engine_t UNUSED axe_engine,
         if (iod_obj_set_scratch(attr_oh, IOD_TID_UNKNOWN, &sp, NULL, NULL) < 0)
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set scratch pad");
 
-        /* Store Metadata in scratch pad */
+        /* Open Metadata KV object for write */
         if (iod_obj_open_write(coh, mdkv_id, NULL, &mdkv_oh, NULL) < 0)
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't create scratch pad");
 
+        /* insert object type metadata */
+        if(H5VL_iod_insert_object_type(mdkv_oh, IOD_TID_UNKNOWN, H5I_ATTR, 
+                                       NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
         /* MSC - need to check size of datatype if it fits in
            entry otherwise create a BLOB*/
-        /* insert datatype metadata into scratch pad */
-        kv.key = strdup("dtype");
-        /* determine the buffer size needed to store the encoded type of the attribute */ 
-        if(H5Tencode(input->type_id, NULL, &buf_size) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode attribute type");
-        if(NULL == (kv.value = malloc (buf_size)))
-            HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate type buffer");
-        /* encode datatype of the attribute */ 
-        if(H5Tencode(input->type_id, kv.value, &buf_size) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode attribute type");
-        kv.value_len = (iod_size_t)buf_size;
-        /* insert kv pair into scratch pad */
-        if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-        free(kv.key);
-        free(kv.value);
-
-        /* insert dataspace metadata into scratch pad */
-        kv.key = strdup("dspace");
-        /* determine the buffer size needed to store the encoded space of the attribute */ 
-        if(H5Sencode(input->space_id, NULL, &buf_size) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode attribute space");
-        if(NULL == (kv.value = malloc (buf_size)))
-            HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate space buffer");
-        /* encode dataspace of the attribute */ 
-        if(H5Sencode(input->space_id, kv.value, &buf_size) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode attribute space");
-        kv.value_len = (iod_size_t)buf_size;
-        /* insert kv pair into scratch pad */
-        if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-        free(kv.key);
-        free(kv.value);
+        /* insert datatype metadata */
+        if(H5VL_iod_insert_datatype(mdkv_oh, IOD_TID_UNKNOWN, input->type_id, 
+                                    NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* insert dataspace metadata */
+        if(H5VL_iod_insert_dataspace(mdkv_oh, IOD_TID_UNKNOWN, input->space_id, 
+                                     NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
 
         /* close the Metadata KV object */
         if(iod_obj_close(mdkv_oh, NULL, NULL))
@@ -174,14 +153,13 @@ H5VL_iod_server_attr_create_cb(AXE_engine_t UNUSED axe_engine,
             HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, FAIL, "can't open scratch pad");
             
         /* insert new attribute in scratch pad of current object */
-        kv.key = HDstrdup(attr_name);
-        kv.value = &attr_id;
-        kv.value_len = 0;
-        if (iod_kv_set(attr_kv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-        HDfree(kv.key);
-
-        iod_obj_close(attr_kv_oh, NULL, NULL);
+        if(H5VL_iod_insert_new_link(attr_kv_oh, IOD_TID_UNKNOWN, attr_name, attr_id, 
+                                    NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* close the Attribute KV object */
+        if(iod_obj_close(attr_kv_oh, NULL, NULL))
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't close object");
     }
 
     /* close parent group if it is not the location we started the
@@ -244,17 +222,16 @@ H5VL_iod_server_attr_open_cb(AXE_engine_t UNUSED axe_engine,
     op_data_t *op_data = (op_data_t *)_op_data;
     attr_open_in_t *input = (attr_open_in_t *)op_data->input;
     attr_open_out_t output;
-    iod_handle_t coh = input->coh;
-    iod_handle_t loc_handle = input->loc_oh;
-    iod_obj_id_t loc_id = input->loc_id;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t loc_handle = input->loc_oh; /* location handle to start traversal */
+    iod_obj_id_t loc_id = input->loc_id; /* location ID */
     iod_handle_t attr_kv_oh, cur_oh, mdkv_oh;
     iod_obj_id_t cur_id, mdkv_id;
     iod_obj_id_t attr_id;
-    const char *loc_name = input->path;
-    const char *attr_name = input->attr_name;
-    char *last_comp = NULL;
+    const char *loc_name = input->path; /* current  path to start traversal */
+    const char *attr_name = input->attr_name; /* attribute's name to open */
+    char *last_comp = NULL; /* name of last object in path */
     scratch_pad_t sp;
-    iod_size_t kv_size = 0;
     herr_t ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI_NOINIT
@@ -311,34 +288,13 @@ H5VL_iod_server_attr_open_cb(AXE_engine_t UNUSED axe_engine,
         HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "can't open scratch pad");
 
 #if 0
-    /* read the attributes's datatype */
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dtype", NULL, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "dtype lookup failed");
-    if(NULL == (buf = H5MM_malloc (kv_size)))
-        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate dtype buffer");
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dtype", buf, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "attribute dtype lookup failed");
-    if((output.type_id = H5Tdecode(buf)) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode datatype");
-    free(buf);
-    buf = NULL;
-
-    kv_size = 0;
-    /* read the attributes's dataspace */
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dspace", NULL, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "dspace lookup failed");
-    if(NULL == (buf = H5MM_malloc (kv_size)))
-        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate dspace buffer");
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dspace", buf, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "attribute dspace lookup failed");
-    if((output.space_id = H5Tdecode(buf)) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode dataspace");
-    free(buf);
-    buf = NULL;
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_DATATYPE, "datatype",
+                             NULL, NULL, NULL, &output.type_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve datatype");
+
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_DATASPACE, "dataspace",
+                             NULL, NULL, NULL, &output.space_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve dataspace");
 #endif
 
     /* close the metadata scratch pad */
@@ -417,22 +373,24 @@ H5VL_iod_server_attr_read_cb(AXE_engine_t UNUSED axe_engine,
 {
     op_data_t *op_data = (op_data_t *)_op_data;
     attr_io_in_t *input = (attr_io_in_t *)op_data->input;
-    iod_handle_t coh = input->coh;
-    iod_handle_t iod_oh = input->iod_oh;
-    iod_obj_id_t iod_id = input->iod_id; 
-    hg_bulk_t bulk_handle = input->bulk_handle;
-    hid_t type_id = input->type_id;
-    hg_bulk_block_t bulk_block_handle;
-    hg_bulk_request_t bulk_request;
-    iod_mem_desc_t mem_desc;
-    iod_array_iodesc_t file_desc;
-    iod_hyperslab_t hslabs;
-    size_t size;
-    void *buf;
-    hid_t space_id;
-    hssize_t num_descriptors = 0;
-    na_addr_t dest = HG_Handler_get_addr(op_data->hg_handle);
-    hbool_t opened_locally = FALSE;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t iod_oh = input->iod_oh; /* attribute's object handle */
+    iod_obj_id_t iod_id = input->iod_id; /* attribute's ID */
+    hg_bulk_t bulk_handle = input->bulk_handle; /* bulk handle for data */
+    hid_t type_id = input->type_id; /* datatype ID of data */
+    hg_bulk_block_t bulk_block_handle; /* HG block handle */
+    hg_bulk_request_t bulk_request; /* HG request */
+    iod_mem_desc_t mem_desc; /* memory descriptor used for reading array */
+    iod_array_iodesc_t file_desc; /* file descriptor used to read array */
+    iod_hyperslab_t hslabs; /* IOD hyperslab generated from HDF5 filespace */
+    size_t size; /* size of outgoing bulk data */
+    void *buf; /* buffer to hold outgoing data */
+    hid_t space_id; /* dataspace ID of attribute */
+    iod_handle_t mdkv_oh; /* metadata KV handle of attribute */
+    scratch_pad_t sp;
+    hssize_t num_descriptors = 0; /* number of IOD file descriptors needed to describe filespace selection */
+    na_addr_t dest = HG_Handler_get_addr(op_data->hg_handle); /* destination address to push data to */
+    hbool_t opened_locally = FALSE; /* flag to indicate whether we opened the attribute here or if it was already open */
     herr_t ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI_NOINIT
@@ -449,40 +407,23 @@ H5VL_iod_server_attr_read_cb(AXE_engine_t UNUSED axe_engine,
     if(NULL == (buf = malloc(size)))
         HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate read buffer");
 
-    /* MSC - remove now till we have an IOD */
+    /* MSC - NEED IOD */
 #if 0
-    {
-        iod_handle_t mdkv_oh;
-        scratch_pad_t sp;
-        iod_size_t kv_size = 0;
-        void *space_buf = NULL;
+    /* get scratch pad of the attribute */
+    if(iod_obj_get_scratch(iod_oh, IOD_TID_UNKNOWN, &sp, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, FAIL, "can't get scratch pad for object");
 
-        /* get scratch pad of the attribute */
-        if(iod_obj_get_scratch(iod_oh, IOD_TID_UNKNOWN, &sp, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, FAIL, "can't get scratch pad for object");
+    /* open the metadata scratch pad of the attribute */
+    if (iod_obj_open_write(coh, sp.mdkv_id, NULL /*hints*/, &mdkv_oh, NULL) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "can't open scratch pad");
 
-        /* open the metadata scratch pad of the attribute */
-        if (iod_obj_open_write(coh, sp.mdkv_id, NULL /*hints*/, &mdkv_oh, NULL) < 0)
-            HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "can't open scratch pad");
-
-        /* read the attributes's dataspace */
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dspace", NULL, 
-                            &kv_size, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "dspace lookup failed");
-        if(NULL == (space_buf = H5MM_malloc (kv_size)))
-            HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate dspace buffer");
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dspace", space_buf, 
-                            &kv_size, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "attribute dspace lookup failed");
-        if((space_id = H5Tdecode(space_buf)) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode dataspace");
-        free(space_buf);
-        space_buf = NULL;
-
-        /* close the metadata scratch pad */
-        if(iod_obj_close(mdkv_oh, NULL, NULL))
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't close object");
-    }
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_DATASPACE, "dataspace",
+                             NULL, NULL, NULL, &space_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve dataspace");
+
+    /* close the metadata scratch pad */
+    if(iod_obj_close(mdkv_oh, NULL, NULL))
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't close object");
 
     /* create memory descriptor for reading */
     mem_desc.nfrag = 1;
@@ -580,23 +521,24 @@ H5VL_iod_server_attr_write_cb(AXE_engine_t UNUSED axe_engine,
 {
     op_data_t *op_data = (op_data_t *)_op_data;
     attr_io_in_t *input = (attr_io_in_t *)op_data->input;
-    iod_handle_t coh = input->coh;
-    iod_handle_t iod_oh = input->iod_oh;
-    iod_obj_id_t iod_id = input->iod_id; 
-    hg_bulk_t bulk_handle = input->bulk_handle;
-    hid_t type_id = input->type_id;
-    hg_bulk_block_t bulk_block_handle;
-    hg_bulk_request_t bulk_request;
-    iod_mem_desc_t mem_desc;
-    iod_array_iodesc_t file_desc;
-    iod_hyperslab_t hslabs;
-    size_t size;
-    void *buf;
-    ssize_t ret;
-    hid_t space_id;
-    hssize_t num_descriptors = 0;
-    na_addr_t source = HG_Handler_get_addr(op_data->hg_handle);
-    hbool_t opened_locally = FALSE;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t iod_oh = input->iod_oh; /* attribute's object handle */
+    iod_obj_id_t iod_id = input->iod_id; /* attribute's ID */
+    hg_bulk_t bulk_handle = input->bulk_handle; /* bulk handle for data */
+    hid_t type_id = input->type_id; /* datatype ID of data */
+    hg_bulk_block_t bulk_block_handle; /* HG block handle */
+    hg_bulk_request_t bulk_request; /* HG request */
+    iod_mem_desc_t mem_desc; /* memory descriptor used for writing array */
+    iod_array_iodesc_t file_desc; /* file descriptor used to write array */
+    iod_hyperslab_t hslabs; /* IOD hyperslab generated from HDF5 filespace */
+    size_t size; /* size of outgoing bulk data */
+    void *buf; /* buffer to hold outgoing data */
+    hid_t space_id; /* dataspace ID of attribute */
+    scratch_pad_t sp;
+    iod_handle_t mdkv_oh; /* metadata KV handle of attribute */
+    hssize_t num_descriptors = 0; /* number of IOD file descriptors needed to describe filespace selection*/
+    na_addr_t source = HG_Handler_get_addr(op_data->hg_handle); /* source address to pull data from */
+    hbool_t opened_locally = FALSE; /* flag to indicate whether we opened the attribute here or if it was already opened */
     herr_t ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI_NOINIT
@@ -637,40 +579,23 @@ H5VL_iod_server_attr_write_cb(AXE_engine_t UNUSED axe_engine,
     }
 #endif
 
-    /* MSC - remove now till we have an IOD */
+    /* MSC - NEED IOD */
 #if 0
-    {
-        iod_handle_t mdkv_oh;
-        scratch_pad_t sp;
-        iod_size_t kv_size = 0;
-        void *space_buf = NULL;
+    /* get scratch pad of the attribute */
+    if(iod_obj_get_scratch(iod_oh, IOD_TID_UNKNOWN, &sp, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, FAIL, "can't get scratch pad for object");
 
-        /* get scratch pad of the attribute */
-        if(iod_obj_get_scratch(iod_oh, IOD_TID_UNKNOWN, &sp, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, FAIL, "can't get scratch pad for object");
+    /* open the metadata scratch pad of the attribute */
+    if (iod_obj_open_write(coh, sp.mdkv_id, NULL /*hints*/, &mdkv_oh, NULL) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "can't open scratch pad");
 
-        /* open the metadata scratch pad of the attribute */
-        if (iod_obj_open_write(coh, sp.mdkv_id, NULL /*hints*/, &mdkv_oh, NULL) < 0)
-            HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "can't open scratch pad");
-
-        /* read the attributes's dataspace */
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dspace", NULL, 
-                            &kv_size, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "dspace lookup failed");
-        if(NULL == (space_buf = H5MM_malloc (kv_size)))
-            HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate dspace buffer");
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dspace", space_buf, 
-                            &kv_size, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "attribute dspace lookup failed");
-        if((space_id = H5Tdecode(space_buf)) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode dataspace");
-        free(space_buf);
-        space_buf = NULL;
-
-        /* close the metadata scratch pad */
-        if(iod_obj_close(mdkv_oh, NULL, NULL))
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't close object");
-    }
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_DATASPACE, "dataspace",
+                             NULL, NULL, NULL, &space_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve dataspace");
+
+    /* close the metadata scratch pad */
+    if(iod_obj_close(mdkv_oh, NULL, NULL))
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't close object");
 
     mem_desc.nfrag = 1;
     mem_desc.frag->addr = buf;
@@ -745,14 +670,15 @@ H5VL_iod_server_attr_exists_cb(AXE_engine_t UNUSED axe_engine,
 {
     op_data_t *op_data = (op_data_t *)_op_data;
     attr_op_in_t *input = (attr_op_in_t *)op_data->input;
-    iod_handle_t coh = input->coh;
-    iod_handle_t loc_handle = input->loc_oh;
-    iod_obj_id_t loc_id = input->loc_id;
-    iod_handle_t cur_oh, attr_kv_oh;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t loc_handle = input->loc_oh; /* location handle to start lookup */
+    iod_obj_id_t loc_id = input->loc_id; /* The ID of the current location object */
+    iod_handle_t cur_oh; /* current object handle accessed */
+    iod_handle_t attr_kv_oh; /* KV handle holding attributes for object */
     iod_obj_id_t cur_id, attr_id;
-    const char *loc_name = input->path;
-    const char *attr_name = input->attr_name;
-    char *last_comp = NULL;
+    const char *loc_name = input->path; /* path to start hierarchy traversal */
+    const char *attr_name = input->attr_name; /* attribute's name */
+    char *last_comp = NULL; /* the last component's name where attribute is created */
     scratch_pad_t sp;
     htri_t ret = -1;
     herr_t ret_value = SUCCEED;
@@ -847,17 +773,18 @@ H5VL_iod_server_attr_rename_cb(AXE_engine_t UNUSED axe_engine,
 {
     op_data_t *op_data = (op_data_t *)_op_data;
     attr_rename_in_t *input = (attr_rename_in_t *)op_data->input;
-    iod_handle_t coh = input->coh;
-    iod_handle_t loc_handle = input->loc_oh;
-    iod_obj_id_t loc_id = input->loc_id;
-    iod_handle_t cur_oh, attr_kv_oh;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t loc_handle = input->loc_oh; /* location handle to start lookup */
+    iod_obj_id_t loc_id = input->loc_id; /* The ID of the current location object */
+    iod_handle_t cur_oh; /* current object handle accessed */
+    iod_handle_t attr_kv_oh; /* KV handle holding attributes for object */
     iod_obj_id_t cur_id, attr_id;
-    const char *loc_name = input->path;
+    const char *loc_name = input->path; /* path to start hierarchy traversal */
     const char *old_name = input->old_attr_name;
     const char *new_name = input->new_attr_name;
-    char *last_comp = NULL;
-    iod_kv_params_t kvs;
-    iod_kv_t kv;
+    char *last_comp = NULL; /* the last component's name where attribute is created */
+    iod_kv_params_t kvs; /* KV lists for objects - used to unlink attribute object */
+    iod_kv_t kv; /* KV entry */
     scratch_pad_t sp;
     herr_t ret_value = SUCCEED;
 
@@ -905,18 +832,17 @@ H5VL_iod_server_attr_rename_cb(AXE_engine_t UNUSED axe_engine,
     kv.value = &attr_id;
     kv.value_len = sizeof(iod_obj_id_t);
     kvs.kv = &kv;
-    if(iod_kv_unlink_keys(attr_kv_oh,IOD_TID_UNKNOWN, NULL, 1, &kvs, NULL) < 0)
+    if(iod_kv_unlink_keys(attr_kv_oh, IOD_TID_UNKNOWN, NULL, 1, &kvs, NULL) < 0)
         HGOTO_ERROR(H5E_SYM, H5E_CANTDEC, FAIL, "Unable to unlink KV pair");
 
     /* insert attribute with new name */
-    kv.key = strdup(new_name);
-    kv.value = &attr_id;
-    kv.value_len = sizeof(iod_obj_id_t);
-    if (iod_kv_set(attr_kv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-    HDfree(kv.key);
+    if(H5VL_iod_insert_new_link(attr_kv_oh, IOD_TID_UNKNOWN, new_name, attr_id, 
+                                NULL, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
 
-    iod_obj_close(attr_kv_oh, NULL, NULL);
+    /* close the Attribute KV object */
+    if(iod_obj_close(attr_kv_oh, NULL, NULL))
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't close object");
 
 #if H5_DO_NATIVE
     ret_value = H5Arename(loc_handle.cookie, old_name, new_name);
@@ -959,14 +885,15 @@ H5VL_iod_server_attr_remove_cb(AXE_engine_t UNUSED axe_engine,
 {
     op_data_t *op_data = (op_data_t *)_op_data;
     attr_op_in_t *input = (attr_op_in_t *)op_data->input;
-    iod_handle_t coh = input->coh;
-    iod_handle_t loc_handle = input->loc_oh;
-    iod_obj_id_t loc_id = input->loc_id;
-    iod_handle_t cur_oh, attr_kv_oh;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t loc_handle = input->loc_oh; /* location handle to start lookup */
+    iod_obj_id_t loc_id = input->loc_id; /* The ID of the current location object */
+    iod_handle_t cur_oh; /* current object handle accessed */
+    iod_handle_t attr_kv_oh; /* KV handle holding attributes for object */
     iod_obj_id_t cur_id, attr_id;
-    const char *loc_name = input->path;
-    const char *attr_name = input->attr_name;
-    char *last_comp = NULL;
+    const char *loc_name = input->path; /* path to start hierarchy traversal */
+    const char *attr_name = input->attr_name; /* attribute's name */
+    char *last_comp = NULL; /* the last component's name where attribute is created */
     iod_kv_params_t kvs;
     iod_kv_t kv;
     scratch_pad_t sp;
@@ -1062,8 +989,8 @@ H5VL_iod_server_attr_close_cb(AXE_engine_t UNUSED axe_engine,
 {
     op_data_t *op_data = (op_data_t *)_op_data;
     attr_close_in_t *input = (attr_close_in_t *)op_data->input;
-    iod_handle_t iod_oh = input->iod_oh;
-    iod_obj_id_t iod_id = input->iod_id; 
+    iod_handle_t iod_oh = input->iod_oh; /* iod handle to close */
+    iod_obj_id_t iod_id = input->iod_id; /* iod id of object to close */
     herr_t ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI_NOINIT
diff --git a/src/H5VLiod_dset.c b/src/H5VLiod_dset.c
index 390a0c5..f31d75a 100644
--- a/src/H5VLiod_dset.c
+++ b/src/H5VLiod_dset.c
@@ -47,18 +47,17 @@ H5VL_iod_server_dset_create_cb(AXE_engine_t UNUSED axe_engine,
     op_data_t *op_data = (op_data_t *)_op_data;
     dset_create_in_t *input = (dset_create_in_t *)op_data->input;
     dset_create_out_t output;
-    iod_handle_t coh = input->coh;
-    iod_handle_t loc_handle = input->loc_oh;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t loc_handle = input->loc_oh; /* location handle to start lookup */
     iod_obj_id_t loc_id = input->loc_id; /* The ID of the current location object */
     iod_obj_id_t dset_id = input->dset_id; /* The ID of the dataset that needs to be created */
     iod_handle_t dset_oh, cur_oh, mdkv_oh;
     iod_obj_id_t cur_id, mdkv_id, attr_id;
-    const char *name = input->name;
+    const char *name = input->name; /* name of dset including path to create */
     char *last_comp; /* the name of the dataset obtained from the last component in the path */
-    iod_kv_t kv;
-    iod_array_struct_t array;
+    hid_t dcpl_id;
+    iod_array_struct_t array; /* IOD array struct describing the dataset's dimensions */
     iod_size_t *max_dims;
-    size_t buf_size;
     scratch_pad_t sp;
     iod_ret_t ret;
     hbool_t collective = FALSE; /* MSC - change when we allow for collective */
@@ -135,97 +134,50 @@ H5VL_iod_server_dset_create_cb(AXE_engine_t UNUSED axe_engine,
         if (iod_obj_set_scratch(dset_oh, IOD_TID_UNKNOWN, &sp, NULL, NULL) < 0)
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set scratch pad");
 
-        /* Store Metadata in scratch pad */
+        /* Open Metadata KV object for write */
         if (iod_obj_open_write(coh, mdkv_id, NULL, &mdkv_oh, NULL) < 0)
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't create scratch pad");
 
-        {
-            size_t buf_size;
-            hid_t dcpl_id;
-            uint64_t count;
-
-            if(H5P_DEFAULT == input->dcpl_id)
-                dcpl_id = H5P_DATASET_CREATE_DEFAULT;
-            else
-                dcpl_id = input->dcpl_id;
-
-            /* insert dataset creation properties in Metadata KV */
-            kv.key = strdup("dcpl");
-            /* determine the buffer size needed to store the encoded dcpl of the dataset */ 
-            if(H5Pencode(dcpl_id,  NULL, &buf_size) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode dataset dcpl");
-            if(NULL == (kv.value = malloc (buf_size)))
-                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate dcpl buffer");
-            /* encode dcpl of the dataset */ 
-            if(H5Pencode(dcpl_id, kv.value, &buf_size) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode dataset dcpl");
-            kv.value_len = (iod_size_t)buf_size;
-            /* insert kv pair into scratch pad */
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-            free(kv.value);
-
-            /* MSC - need to check size of datatype if it fits in
-               entry otherwise create a BLOB*/
-            /* insert datatype metadata into scratch pad */
-            kv.key = strdup("dtype");
-            /* determine the buffer size needed to store the encoded type of the dataset */ 
-            if(H5Tencode(input->type_id, NULL, &buf_size) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode dataset type");
-            if(NULL == (kv.value = malloc (buf_size)))
-                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate type buffer");
-            /* encode datatype of the dataset */ 
-            if(H5Tencode(input->type_id, kv.value, &buf_size) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode dataset type");
-            kv.value_len = (iod_size_t)buf_size;
-            /* insert kv pair into scratch pad */
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-            free(kv.value);
-
-            /* insert dataspace metadata into scratch pad */
-            kv.key = strdup("dspace");
-            /* determine the buffer size needed to store the encoded space of the dataset */ 
-            if(H5Sencode(input->space_id, NULL, &buf_size) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode dataset space");
-            if(NULL == (kv.value = malloc (buf_size)))
-                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate space buffer");
-            /* encode dataspace of the dataset */ 
-            if(H5Sencode(input->space_id, kv.value, &buf_size) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode dataset space");
-            kv.value_len = (iod_size_t)buf_size;
-            /* insert kv pair into scratch pad */
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-            free(kv.value);
-
-            /* insert link count metadata on object */
-            if(NULL == (kv.value = malloc (sizeof(uint64_t))))
-                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate buffer");
-            /* initial count is 1, since object is created now */
-            count = 1;
-            memcpy(kv.value, &count, sizeof(uint64_t));
-            kv.key = strdup("link_count");
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-            free(kv.value);
-        }
+        if(H5P_DEFAULT == input->dcpl_id)
+            dcpl_id = H5P_DATASET_CREATE_DEFAULT;
+        else
+            dcpl_id = input->dcpl_id;
+
+        /* insert plist metadata */
+        if(H5VL_iod_insert_plist(mdkv_oh, IOD_TID_UNKNOWN, dcpl_id, 
+                                 NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* insert link count metadata */
+        if(H5VL_iod_insert_link_count(mdkv_oh, IOD_TID_UNKNOWN, (uint64_t)1, 
+                                      NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* insert object type metadata */
+        if(H5VL_iod_insert_object_type(mdkv_oh, IOD_TID_UNKNOWN, H5I_DATASET, 
+                                       NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* MSC - need to check size of datatype if it fits in
+           entry otherwise create a BLOB*/
+        /* insert datatype metadata */
+        if(H5VL_iod_insert_datatype(mdkv_oh, IOD_TID_UNKNOWN, input->type_id, 
+                                    NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* insert dataspace metadata */
+        if(H5VL_iod_insert_dataspace(mdkv_oh, IOD_TID_UNKNOWN, input->space_id, 
+                                     NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
 
         /* close the Metadata KV object */
         if(iod_obj_close(mdkv_oh, NULL, NULL))
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't close object");
 
-        kv.key = strdup(last_comp);
-        kv.value = &dset_id;
-        kv.value_len = sizeof(iod_obj_id_t);
-        /* insert new dataset in kv store of current group */
-        if (iod_kv_set(cur_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-        free(kv.key);
+        /* add link in parent group to current object */
+        if(H5VL_iod_insert_new_link(cur_oh, IOD_TID_UNKNOWN, last_comp, dset_id, 
+                                    NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
     }
 
     /* close parent group if it is not the location we started the
@@ -288,17 +240,15 @@ H5VL_iod_server_dset_open_cb(AXE_engine_t UNUSED axe_engine,
     op_data_t *op_data = (op_data_t *)_op_data;
     dset_open_in_t *input = (dset_open_in_t *)op_data->input;
     dset_open_out_t output;
-    iod_handle_t coh = input->coh;
-    iod_handle_t loc_handle = input->loc_oh;
-    iod_obj_id_t loc_id = input->loc_id;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t loc_handle = input->loc_oh; /* location handle to start lookup */
+    iod_obj_id_t loc_id = input->loc_id; /* The ID of the current location object */
+    iod_obj_id_t dset_id; /* ID of the dataset to open */
+    char *name = input->name; /* name of dset including path to open */
+    char *last_comp; /* the name of the dataset obtained from the last component in the path */
     iod_handle_t cur_oh, mdkv_oh;
     iod_obj_id_t cur_id;
-    iod_obj_id_t dset_id;
-    char *name = input->name;
-    char *last_comp;
-    void *buf = NULL;
     scratch_pad_t sp;
-    iod_size_t kv_size;
     herr_t ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI_NOINIT
@@ -314,10 +264,8 @@ H5VL_iod_server_dset_open_cb(AXE_engine_t UNUSED axe_engine,
                                 &last_comp, &cur_id, &cur_oh) < 0)
         HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't traverse path");
 
-    kv_size = sizeof(iod_obj_id_t);
-
     if(iod_kv_get_value(cur_oh, IOD_TID_UNKNOWN, last_comp, &dset_id, 
-                        kv_size , NULL, NULL) < 0)
+                        sizeof(iod_obj_id_t), NULL, NULL) < 0)
         HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "can't retrieve Array ID from parent KV store");
 
     /* close parent group and its scratch pad if it is not the
@@ -338,58 +286,23 @@ H5VL_iod_server_dset_open_cb(AXE_engine_t UNUSED axe_engine,
     if (iod_obj_open_write(coh, sp.mdkv_id, NULL /*hints*/, &mdkv_oh, NULL) < 0)
         HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "can't open scratch pad");
 
-    /* MSC - retrieve metadata */
+    /* MSC - retrieve metadata - NEED IOD */
 #if 0
-    kv_size = 0;
-    /* read the datasets's creation properties */
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dcpl", NULL, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "dcpl lookup failed");
-    if(NULL == (buf = malloc (kv_size)))
-        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate dcpl buffer");
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dcpl", buf, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "dcpl lookup failed");
-    if((output.dcpl_id = H5Pdecode(buf)) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode dcpl");
-    free(buf);
-    buf = NULL;
-
-    kv_size = 0;
-    /* read the datasets's datatype */
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dtype", NULL, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "dtype lookup failed");
-    if(NULL == (buf = H5MM_malloc (kv_size)))
-        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate dtype buffer");
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dtype", buf, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "dataset dtype lookup failed");
-    if((output.type_id = H5Tdecode(buf)) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode datatype");
-    free(buf);
-    buf = NULL;
-
-    kv_size = 0;
-    /* read the datasets's dataspace */
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dspace", NULL, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "dspace lookup failed");
-    if(NULL == (buf = H5MM_malloc (kv_size)))
-        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate dspace buffer");
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "dspace", buf, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "dataset dspace lookup failed");
-    if((output.space_id = H5Tdecode(buf)) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode dataspace");
-    free(buf);
-    buf = NULL;
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_PLIST, "create_plist",
+                             NULL, NULL, NULL, &output.dcpl_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve dcpl");
+
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_LINK_COUNT, "link_count",
+                             NULL, NULL, NULL, &output.link_count) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve link count");
 
-    kv_size = sizeof(uint64_t);
-    /* read the dataset's link count */
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "link_count", output.link_count, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "link_count lookup failed");
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_DATATYPE, "datatype",
+                             NULL, NULL, NULL, &output.type_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve datatype");
+
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_DATASPACE, "dataspace",
+                             NULL, NULL, NULL, &output.space_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve dataspace");
 #endif
 
     /* close the metadata scratch pad */
@@ -491,28 +404,28 @@ H5VL_iod_server_dset_read_cb(AXE_engine_t UNUSED axe_engine,
     op_data_t *op_data = (op_data_t *)_op_data;
     dset_io_in_t *input = (dset_io_in_t *)op_data->input;
     dset_read_out_t output;
-    iod_handle_t coh = input->coh;
-    iod_handle_t iod_oh = input->iod_oh;
-    iod_obj_id_t iod_id = input->iod_id;    
-    hg_bulk_t bulk_handle = input->bulk_handle;
-    hid_t space_id = input->space_id;
-    hid_t dxpl_id = input->dxpl_id;
-    hid_t src_id = input->dset_type_id;
-    hid_t dst_id = input->mem_type_id;
-    hg_bulk_block_t bulk_block_handle;
-    hg_bulk_request_t bulk_request;
-    iod_mem_desc_t mem_desc;
-    iod_array_iodesc_t file_desc;
-    iod_hyperslab_t *hslabs = NULL;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t iod_oh = input->iod_oh; /* dset object handle */
+    iod_obj_id_t iod_id = input->iod_id; /* dset ID */
+    hg_bulk_t bulk_handle = input->bulk_handle; /* bulk handle for data */
+    hid_t space_id = input->space_id; /* file space selection */
+    hid_t dxpl_id = input->dxpl_id; /* transfer property list */
+    hid_t src_id = input->dset_type_id; /* the datatype of the dataset's element */
+    hid_t dst_id = input->mem_type_id; /* the memory type of the elements */
+    hg_bulk_block_t bulk_block_handle; /* HG block handle */
+    hg_bulk_request_t bulk_request; /* HG request */
+    iod_mem_desc_t mem_desc; /* memory descriptor used for reading array */
+    iod_array_iodesc_t file_desc; /* file descriptor used to read array */
+    iod_hyperslab_t *hslabs = NULL; /* IOD hyperslab generated from HDF5 filespace */
     size_t size, buf_size, src_size, dst_size;
-    void *buf;
+    void *buf; /* buffer to hold outgoing data */
     uint8_t *buf_ptr;
-    hssize_t num_descriptors = 0, n;
-    int ndims, i;
-    uint32_t cs = 0;
-    size_t nelmts;
-    na_addr_t dest = HG_Handler_get_addr(op_data->hg_handle);
-    hbool_t opened_locally = FALSE;
+    hssize_t num_descriptors = 0, n; /* number of IOD file descriptors needed to describe filespace selection */
+    int ndims, i; /* dataset's rank/number of dimensions */
+    uint32_t cs = 0; /* checksum value */
+    size_t nelmts; /* number of elements selected to read */
+    na_addr_t dest = HG_Handler_get_addr(op_data->hg_handle); /* destination address to push data to */
+    hbool_t opened_locally = FALSE; /* flag to indicate whether we opened the dset here or if it was already open */
     herr_t ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI_NOINIT
@@ -702,30 +615,30 @@ H5VL_iod_server_dset_write_cb(AXE_engine_t UNUSED axe_engine,
 {
     op_data_t *op_data = (op_data_t *)_op_data;
     dset_io_in_t *input = (dset_io_in_t *)op_data->input;
-    iod_handle_t coh = input->coh;
-    iod_handle_t iod_oh = input->iod_oh;
-    iod_obj_id_t iod_id = input->iod_id; 
-    hg_bulk_t bulk_handle = input->bulk_handle;
-    hid_t space_id = input->space_id;
-    hid_t dxpl_id = input->dxpl_id;
-    uint32_t cs = input->checksum;
-    hid_t src_id = input->mem_type_id;
-    hid_t dst_id = input->dset_type_id;
-    uint32_t data_cs = 0;
-    hg_bulk_block_t bulk_block_handle;
-    hg_bulk_request_t bulk_request;
-    iod_mem_desc_t mem_desc;
-    iod_array_iodesc_t file_desc;
-    iod_hyperslab_t *hslabs = NULL;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t iod_oh = input->iod_oh; /* dset object handle */
+    iod_obj_id_t iod_id = input->iod_id; /* dset ID */
+    hg_bulk_t bulk_handle = input->bulk_handle; /* bulk handle for data */
+    hid_t space_id = input->space_id; /* file space selection */
+    hid_t dxpl_id = input->dxpl_id; /* transfer property list */
+    uint32_t cs = input->checksum; /* checksum recieved for data */
+    hid_t src_id = input->mem_type_id; /* the memory type of the elements */
+    hid_t dst_id = input->dset_type_id; /* the datatype of the dataset's element */
+    hg_bulk_block_t bulk_block_handle; /* HG block handle */
+    hg_bulk_request_t bulk_request; /* HG request */
+    iod_mem_desc_t mem_desc; /* memory descriptor used for writing array */
+    iod_array_iodesc_t file_desc; /* file descriptor used to write array */
+    iod_hyperslab_t *hslabs = NULL; /* IOD hyperslab generated from HDF5 filespace */
     size_t size, buf_size, src_size, dst_size;
-    hssize_t num_descriptors = 0, n;
-    int ndims, i;
+    uint32_t data_cs = 0;
+    hssize_t num_descriptors = 0, n; /* number of IOD file descriptors needed to describe filespace selection */
+    int ndims, i; /* dataset's rank/number of dimensions */
     void *buf;
     uint8_t *buf_ptr;
-    size_t nelmts;
-    hbool_t flag = FALSE;
-    na_addr_t source = HG_Handler_get_addr(op_data->hg_handle);
-    hbool_t opened_locally = FALSE;
+    size_t nelmts; /* number of elements selected to write */
+    hbool_t flag = FALSE; /* temp flag to indicate whether corruption will be inserted */
+    na_addr_t source = HG_Handler_get_addr(op_data->hg_handle); /* source address to pull data from */
+    hbool_t opened_locally = FALSE; /* flag to indicate whether we opened the dset here or if it was already open */
     herr_t ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI_NOINIT
@@ -936,7 +849,7 @@ H5VL_iod_server_dset_set_extent_cb(AXE_engine_t UNUSED axe_engine,
     iod_handle_t coh = input->coh;
     iod_handle_t iod_oh = input->iod_oh;
     iod_obj_id_t iod_id = input->iod_id; 
-    int rank = input->dims.rank;
+    int rank = input->dims.rank; /* rank of dataset */
     hbool_t opened_locally = FALSE;
     herr_t ret_value = SUCCEED;
 
diff --git a/src/H5VLiod_dtype.c b/src/H5VLiod_dtype.c
index 454cd03..264ab27 100644
--- a/src/H5VLiod_dtype.c
+++ b/src/H5VLiod_dtype.c
@@ -47,22 +47,22 @@ H5VL_iod_server_dtype_commit_cb(AXE_engine_t UNUSED axe_engine,
     op_data_t *op_data = (op_data_t *)_op_data;
     dtype_commit_in_t *input = (dtype_commit_in_t *)op_data->input;
     dtype_commit_out_t output;
-    iod_handle_t coh = input->coh;
-    iod_handle_t loc_handle = input->loc_oh;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t loc_handle = input->loc_oh; /* location handle to start lookup */
     iod_obj_id_t loc_id = input->loc_id; /* The ID of the current location object */
     iod_obj_id_t dtype_id = input->dtype_id; /* The ID of the datatype that needs to be created */
     iod_handle_t dtype_oh, cur_oh, mdkv_oh;
     iod_obj_id_t cur_id, mdkv_id, attr_id;
-    const char *name = input->name;
-    iod_kv_t kv;
+    const char *name = input->name; /* name of dtype including path to commit */
+    hid_t tcpl_id;
     char *last_comp; /* the name of the datatype obtained from the last component in the path */
-    size_t buf_size;
+    size_t buf_size; /* size of the serialized datatype */
     void *buf;
-    iod_mem_desc_t mem_desc;
-    iod_blob_iodesc_t file_desc;
+    iod_mem_desc_t mem_desc; /* memory descriptor used for writing */
+    iod_blob_iodesc_t file_desc; /* file descriptor used to write */
     scratch_pad_t sp;
     iod_ret_t ret;
-    hbool_t collective = FALSE; /* MSC - change when we allow for collective */
+    hbool_t collective = FALSE; /* flag to indicate whether we opened the attribute here or if it was already open */
     herr_t ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI_NOINIT
@@ -142,67 +142,57 @@ H5VL_iod_server_dtype_commit_cb(AXE_engine_t UNUSED axe_engine,
         if(iod_blob_write(dtype_oh, IOD_TID_UNKNOWN, NULL, &mem_desc, &file_desc, NULL, NULL) < 0)
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "unable to write BLOB object");
 
-        {
-            size_t tcpl_size = 0;
-            hid_t tcpl_id;
-            uint64_t count;
-
-            if(H5P_DEFAULT == input->tcpl_id)
-                tcpl_id = H5P_DATATYPE_CREATE_DEFAULT;
-            else
-                tcpl_id = input->tcpl_id;
-
-            /* insert datatype creation properties in Metadata KV */
-            kv.key = strdup("tcpl");
-            /* determine the buffer size needed to store the encoded tcpl of the datatype */ 
-            if(H5Pencode(tcpl_id,  NULL, &tcpl_size) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode tcpl");
-            if(NULL == (kv.value = malloc (tcpl_size)))
-                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate tcpl buffer");
-            /* encode tcpl of the datatype */ 
-            if(H5Pencode(tcpl_id, kv.value, &tcpl_size) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode tcpl");
-            kv.value_len = (iod_size_t)tcpl_size;
-            /* insert kv pair into scratch pad */
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-            free(kv.value);
 
-            /* insert link count metadata on object */
-            if(NULL == (kv.value = malloc (sizeof(uint64_t))))
-                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate buffer");
-            /* initial count is 1, since object is created now */
-            count = 1;
-            memcpy(kv.value, &count, sizeof(uint64_t));
-            kv.key = strdup("link_count");
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-            free(kv.value);
+        if(H5P_DEFAULT == input->tcpl_id)
+            tcpl_id = H5P_DATATYPE_CREATE_DEFAULT;
+        else
+            tcpl_id = input->tcpl_id;
+
+        /* insert plist metadata */
+        if(H5VL_iod_insert_plist(mdkv_oh, IOD_TID_UNKNOWN, tcpl_id, 
+                                 NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* insert link count metadata */
+        if(H5VL_iod_insert_link_count(mdkv_oh, IOD_TID_UNKNOWN, (uint64_t)1, 
+                                      NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* insert object type metadata */
+        if(H5VL_iod_insert_object_type(mdkv_oh, IOD_TID_UNKNOWN, H5I_DATATYPE, 
+                                       NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
 
-            kv.key = strdup("size");
+        /* store the datatype size */
+        {
+            iod_kv_t kv;
+            char *key = NULL;
+            char *value = NULL;
+
+            key = strdup("size");
+            kv.key = key;
             kv.value_len = sizeof(iod_size_t);
-            if(NULL == (kv.value = malloc (kv.value_len)))
+
+            if(NULL == (value = malloc (kv.value_len)))
                 HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate buffer");
-            memcpy(kv.value, &buf_size, kv.value_len);
+            *((int32_t *)value) = buf_size;
+            kv.value = value;
+
             if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
                 HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-            free(kv.value);
+
+            free(key);
+            free(value);
         }
 
         /* close the Metadata KV object */
         if(iod_obj_close(mdkv_oh, NULL, NULL))
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't close object");
 
-        kv.key = strdup(last_comp);
-        kv.value = &dtype_id;
-        kv.value_len = sizeof(iod_obj_id_t);
-        /* insert new datatype in kv store of current group */
-        if (iod_kv_set(cur_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-        free(kv.key);
+        /* add link in parent group to current object */
+        if(H5VL_iod_insert_new_link(cur_oh, IOD_TID_UNKNOWN, last_comp, dtype_id, 
+                                    NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
     }
 #if H5_DO_NATIVE
     cur_oh.cookie = H5Tcopy(input->type_id);
@@ -264,18 +254,18 @@ H5VL_iod_server_dtype_open_cb(AXE_engine_t UNUSED axe_engine,
     op_data_t *op_data = (op_data_t *)_op_data;
     dtype_open_in_t *input = (dtype_open_in_t *)op_data->input;
     dtype_open_out_t output;
-    iod_handle_t coh = input->coh;
-    iod_handle_t loc_handle = input->loc_oh;
-    iod_obj_id_t loc_id = input->loc_id;
-    iod_obj_id_t dtype_id;
+    iod_handle_t coh = input->coh; /* container handle */
+    iod_handle_t loc_handle = input->loc_oh; /* location handle to start lookup */
+    iod_obj_id_t loc_id = input->loc_id; /* The ID of the current location object */
+    iod_obj_id_t dtype_id; /* ID of datatype to open */
     iod_handle_t cur_oh, mdkv_oh;
     iod_obj_id_t cur_id, mdkv_id;
-    const char *name = input->name;
+    const char *name = input->name; /* name of dtype including path to open */
     char *last_comp; /* the name of the datatype obtained from the last component in the path */
-    size_t buf_size;
-    void *buf = NULL, *tcpl = NULL;
-    iod_mem_desc_t mem_desc;
-    iod_blob_iodesc_t file_desc;
+    size_t buf_size; /* size of serialized datatype */
+    void *buf = NULL;
+    iod_mem_desc_t mem_desc; /* memory descriptor used for reading */
+    iod_blob_iodesc_t file_desc; /* file descriptor used to write */
     iod_size_t kv_size = sizeof(iod_obj_id_t);
     scratch_pad_t sp;
     herr_t ret_value = SUCCEED;
@@ -308,28 +298,15 @@ H5VL_iod_server_dtype_open_cb(AXE_engine_t UNUSED axe_engine,
         HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "can't open scratch pad");
 
 #if 0
-    kv_size = 0;
-    /* read the datatypes's creation properties */
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "tcpl", NULL, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "tcpl lookup failed");
-    if(NULL == (tcpl = malloc (kv_size)))
-        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate tcpl buffer");
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "tcpl", tcpl, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "tcpl lookup failed");
-    if((output.tcpl_id = H5Pdecode(tcpl)) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode tcpl");
-    free(tcpl);
-    tcpl = NULL;
-
-    kv_size = sizeof(uint64_t);
-    /* read the datatype's link count */
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "link_count", output.link_count, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "link_count lookup failed");
-
-    /*retrieve blob size metadata from scratch pad */
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_PLIST, "create_plist",
+                             NULL, NULL, NULL, &output.tcpl_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve tcpl");
+
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_LINK_COUNT, "link_count",
+                             NULL, NULL, NULL, &output.link_count) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve link count");
+
+    /* retrieve blob size metadata from scratch pad */
     if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "size", &buf_size, 
                         sizeof(iod_size_t), NULL, NULL) < 0)
         HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "datatype size lookup failed");
diff --git a/src/H5VLiod_file.c b/src/H5VLiod_file.c
index 94fb4b7..febc379 100644
--- a/src/H5VLiod_file.c
+++ b/src/H5VLiod_file.c
@@ -49,10 +49,11 @@ H5VL_iod_server_file_create_cb(AXE_engine_t UNUSED axe_engine,
     op_data_t *op_data = (op_data_t *)_op_data;
     file_create_in_t *input = (file_create_in_t *)op_data->input;
     file_create_out_t output;
-    unsigned int mode;
-    iod_handle_t coh;
-    iod_handle_t root_oh, mdkv_oh;
-    iod_obj_id_t mdkv_id, attr_id;
+    unsigned int mode; /* create mode */
+    iod_handle_t coh; /* container handle */
+    iod_handle_t root_oh; /* root object handle */
+    iod_handle_t mdkv_oh; /* metadata object handle for KV to store file's metadata */
+    iod_obj_id_t mdkv_id, attr_id; /* metadata and attribute KV IDs for the file */
     iod_ret_t ret;
     herr_t ret_value = SUCCEED;
 
@@ -87,6 +88,12 @@ H5VL_iod_server_file_create_cb(AXE_engine_t UNUSED axe_engine,
        the scratch pad for it too */
     if(0 == ret) {
         scratch_pad_t sp;
+        iod_kv_t kv;
+        void *key = NULL;
+        void *value = NULL;
+        size_t buf_size;
+        hid_t fcpl_id;
+        uint64_t index;
 
         /* create the metadata KV object for the root group */
         if(iod_obj_create(coh, IOD_TID_UNKNOWN, NULL, IOD_OBJ_KV, 
@@ -113,57 +120,47 @@ H5VL_iod_server_file_create_cb(AXE_engine_t UNUSED axe_engine,
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't create scratch pad");
 
         /* store metadata */
-        {
-            iod_kv_t kv;
-            size_t buf_size;
-            hid_t fcpl_id;
-            uint64_t index;
-
-            if(H5P_DEFAULT == input->fcpl_id)
-                fcpl_id = H5P_FILE_CREATE_DEFAULT;
-            else
-                fcpl_id = input->fcpl_id;
-
-            /* insert file creation properties in Metadata KV */
-            kv.key = strdup("fcpl");
-            /* determine the buffer size needed to store the encoded fcpl of the file */ 
-            if(H5Pencode(fcpl_id,  NULL, &buf_size) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode file fcpl");
-            if(NULL == (kv.value = malloc (buf_size)))
-                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate fcpl buffer");
-            /* encode fcpl of the file */ 
-            if(H5Pencode(fcpl_id, kv.value, &buf_size) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode file fcpl");
-            kv.value_len = (iod_size_t)buf_size;
-            /* insert kv pair into scratch pad */
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-            free(kv.value);
-
-            /* insert initial indexes for IOD IDs */
-            if(NULL == (kv.value = malloc (sizeof(uint64_t))))
-                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate fcpl buffer");
-            index = 1;
-            memcpy(kv.value, &index, sizeof(uint64_t));
-
-            kv.key = strdup("kv_index");
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-
-            kv.key = strdup("array_index");
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-
-            kv.key = strdup("blob_index");
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-
-            free(kv.value);
-        }
+
+
+        if(H5P_DEFAULT == input->fcpl_id)
+            fcpl_id = H5P_FILE_CREATE_DEFAULT;
+        else
+            fcpl_id = input->fcpl_id;
+
+        /* insert plist metadata */
+        if(H5VL_iod_insert_plist(mdkv_oh, IOD_TID_UNKNOWN, fcpl_id, 
+                                 NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert link count KV value");
+
+        /* insert initial indexes for IOD IDs */
+        if(NULL == (value = malloc (sizeof(uint64_t))))
+            HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate buffer");
+        *((uint64_t *)value) = 1;
+        kv.value_len = sizeof(uint64_t);
+
+        key = strdup("kv_index");
+        kv.key = (char *)key;
+        if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
+        free(key); 
+        key = NULL;
+
+        key = strdup("array_index");
+        kv.key = (char *)key;
+        if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
+        free(key); 
+        key = NULL;
+
+        key = strdup("blob_index");
+        kv.key = (char *)key;
+        if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
+        free(key); 
+        key = NULL;
+
+        free(value); 
+        value = NULL;
 
         if(iod_obj_close(mdkv_oh, NULL, NULL))
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't close root object handle");
@@ -227,9 +224,10 @@ H5VL_iod_server_file_open_cb(AXE_engine_t UNUSED axe_engine,
     op_data_t *op_data = (op_data_t *)_op_data;
     file_open_in_t *input = (file_open_in_t *)op_data->input;
     file_open_out_t output;
-    unsigned int mode = input->flags;
-    iod_handle_t coh;
-    iod_handle_t root_oh, mdkv_oh;
+    unsigned int mode = input->flags; /* File Open mode */
+    iod_handle_t coh; /* container handle */
+    iod_handle_t root_oh; /* root object handle */
+    iod_handle_t mdkv_oh; /* metadata object handle for KV to store file's metadata */
     scratch_pad_t sp;
     herr_t ret_value = SUCCEED;
 
@@ -262,35 +260,23 @@ H5VL_iod_server_file_open_cb(AXE_engine_t UNUSED axe_engine,
     output.blob_oid_index = 1;
     output.fcpl_id = H5P_FILE_CREATE_DEFAULT;
 
+    /* MSC - NEED IOD */
 #if 0
-    {
-        void *fcpl_buf = NULL;
-        size_t fcpl_size = 0;
-
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "fcpl", NULL, 
-                            &fcpl_size, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "file fcpl lookup failed");
-        if(NULL == (fcpl_buf = H5MM_malloc (output.fcpl_size)))
-            HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate fcpl buffer");
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "file_fcpl", fcpl_buf, 
-                            &fcpl_size, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "file fcpl lookup failed");
-        if((output.fcpl_id = H5Pdecode(fcpl_buf)) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode file fcpl");
-        free(fcpl_buf);
-
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "kv_index", &output.kv_oid_index, 
-                            sizeof(uint64_t), NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "KV index lookup failed");
-
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "array_index", &output.array_oid_index, 
-                            sizeof(uint64_t), NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "Array index lookup failed");
-
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "blob_index", &output.blob_oid_index, 
-                            sizeof(uint64_t), NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "BLOB index lookup failed");
-    }
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_PLIST, "create_plist",
+                             NULL, NULL, NULL, &output.fcpl_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve fcpl");
+
+    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "kv_index", &output.kv_oid_index, 
+                        sizeof(uint64_t), NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "KV index lookup failed");
+
+    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "array_index", &output.array_oid_index, 
+                        sizeof(uint64_t), NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "Array index lookup failed");
+
+    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "blob_index", &output.blob_oid_index, 
+                        sizeof(uint64_t), NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "BLOB index lookup failed");
 #endif
 
     /* close the metadata scratch pad */
diff --git a/src/H5VLiod_group.c b/src/H5VLiod_group.c
index b830079..018457d 100644
--- a/src/H5VLiod_group.c
+++ b/src/H5VLiod_group.c
@@ -57,7 +57,7 @@ H5VL_iod_server_group_create_cb(AXE_engine_t UNUSED axe_engine,
     iod_handle_t grp_oh, cur_oh, mdkv_oh;
     iod_obj_id_t cur_id, mdkv_id, attr_id;
     char *last_comp; /* the name of the group obtained from traversal function */
-    iod_kv_t kv;
+    hid_t gcpl_id;
     scratch_pad_t sp;
     iod_ret_t ret;
     hbool_t collective = FALSE; /* MSC - change when we allow for collective */
@@ -111,62 +111,39 @@ H5VL_iod_server_group_create_cb(AXE_engine_t UNUSED axe_engine,
         if (iod_obj_set_scratch(grp_oh, IOD_TID_UNKNOWN, &sp, NULL, NULL) < 0)
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set scratch pad");
 
-        /* Store Metadata in scratch pad */
+        /* store metadata */
+        /* Open Metadata KV object for write */
         if (iod_obj_open_write(coh, mdkv_id, NULL, &mdkv_oh, NULL) < 0)
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't create scratch pad");
 
-        /* store metadata */
-        {
-            iod_kv_t kv;
-            size_t buf_size;
-            hid_t gcpl_id;
-            uint64_t count;
-
-            if(H5P_DEFAULT == input->gcpl_id)
-                gcpl_id = H5P_GROUP_CREATE_DEFAULT;
-            else
-                gcpl_id = input->gcpl_id;
-
-            /* insert group creation properties in Metadata KV */
-            kv.key = strdup("gcpl");
-            /* determine the buffer size needed to store the encoded gcpl of the group */ 
-            if(H5Pencode(gcpl_id,  NULL, &buf_size) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode group gcpl");
-            if(NULL == (kv.value = malloc (buf_size)))
-                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate gcpl buffer");
-            /* encode gcpl of the group */ 
-            if(H5Pencode(gcpl_id, kv.value, &buf_size) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode group gcpl");
-            kv.value_len = (iod_size_t)buf_size;
-            /* insert kv pair into scratch pad */
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-            free(kv.value);
-
-            /* insert link count metadata on object */
-            if(NULL == (kv.value = malloc (sizeof(uint64_t))))
-                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate buffer");
-            /* initial count is 1, since object is created now */
-            count = 1;
-            memcpy(kv.value, &count, sizeof(uint64_t));
-            kv.key = strdup("link_count");
-            if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-            free(kv.key);
-            free(kv.value);
-        }
+        if(H5P_DEFAULT == input->gcpl_id)
+            gcpl_id = H5P_GROUP_CREATE_DEFAULT;
+        else
+            gcpl_id = input->gcpl_id;
+
+        /* insert plist metadata */
+        if(H5VL_iod_insert_plist(mdkv_oh, IOD_TID_UNKNOWN, gcpl_id, 
+                                 NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* insert link count metadata */
+        if(H5VL_iod_insert_link_count(mdkv_oh, IOD_TID_UNKNOWN, (uint64_t)1, 
+                                      NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
 
+        /* insert object type metadata */
+        if(H5VL_iod_insert_object_type(mdkv_oh, IOD_TID_UNKNOWN, H5I_GROUP, 
+                                       NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* close Metadata KV object */
         if(iod_obj_close(mdkv_oh, NULL, NULL))
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't close object");
 
-        /* insert new group in kv store of parent object */
-        kv.key = strdup(last_comp);
-        kv.value = &grp_id;
-        kv.value_len = sizeof(iod_obj_id_t);
-        if (iod_kv_set(cur_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-        free(kv.key);
+        /* add link in parent group to current object */
+        if(H5VL_iod_insert_new_link(cur_oh, IOD_TID_UNKNOWN, last_comp, grp_id, 
+                                    NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
     } /* end if */
 
     /* close parent group if it is not the location we started the
@@ -228,12 +205,12 @@ H5VL_iod_server_group_open_cb(AXE_engine_t UNUSED axe_engine,
     group_open_in_t *input = (group_open_in_t *)op_data->input;
     group_open_out_t output;
     iod_handle_t coh = input->coh;
-    iod_handle_t loc_handle = input->loc_oh;
-    iod_obj_id_t loc_id = input->loc_id;
-    const char *name = input->name;
+    iod_handle_t loc_handle = input->loc_oh; /* location handle to start lookup */
+    iod_obj_id_t loc_id = input->loc_id; /* The ID of the current location object */
+    const char *name = input->name; /* group name including path to open */
     iod_obj_id_t grp_id; /* The ID of the group that needs to be opened */
     iod_handle_t cur_oh, mdkv_oh;
-    iod_obj_id_t cur_id, mdkv_id;
+    iod_obj_id_t cur_id;
     char *last_comp; /* the name of the group obtained from traversal function */
     iod_size_t kv_size;
     scratch_pad_t sp;
@@ -277,31 +254,15 @@ H5VL_iod_server_group_open_cb(AXE_engine_t UNUSED axe_engine,
     if (iod_obj_open_write(coh, sp.mdkv_id, NULL /*hints*/, &mdkv_oh, NULL) < 0)
         HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "can't open scratch pad");
 
-    /* MSC - retrieve metadata */
-#if 0 
-    {
-        void *buf = NULL;
-
-        kv_size = 0;
-        /* read the group's creation properties */
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "gcpl", NULL, 
-                            &kv_size, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "group gcpl lookup failed");
-        if(NULL == (buf = malloc (kv_size)))
-            HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate gcpl buffer");
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "gcpl", buf, 
-                            &kv_size, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "group gcpl lookup failed");
-        if((output.gcpl_id = H5Pdecode(buf)) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode gcpl");
-        free(buf);
-
-        kv_size = sizeof(uint64_t);
-        /* read the group's link count */
-        if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "link_count", output.link_count, 
-                            &kv_size, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "link_count lookup failed");
-    }
+    /* MSC - retrieve metadata, need IOD */
+#if 0
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_PLIST, "create_plist",
+                             NULL, NULL, NULL, &output.gcpl_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve gcpl");
+
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_LINK_COUNT, "link_count",
+                             NULL, NULL, NULL, &output.link_count) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve link count");
 #endif
 
     /* close the metadata scratch pad */
diff --git a/src/H5VLiod_map.c b/src/H5VLiod_map.c
index a96b9e9..002d315 100644
--- a/src/H5VLiod_map.c
+++ b/src/H5VLiod_map.c
@@ -59,10 +59,8 @@ H5VL_iod_server_map_create_cb(AXE_engine_t UNUSED axe_engine,
     iod_handle_t map_oh, cur_oh, mdkv_oh;
     iod_obj_id_t cur_id, mdkv_id, attr_id;
     char *last_comp; /* the name of the group obtained from traversal function */
-    iod_kv_t kv;
     scratch_pad_t sp;
     iod_ret_t ret;
-    uint64_t count;
     hbool_t collective = FALSE; /* MSC - change when we allow for collective */
     herr_t ret_value = SUCCEED;
 
@@ -114,32 +112,31 @@ H5VL_iod_server_map_create_cb(AXE_engine_t UNUSED axe_engine,
         if (iod_obj_set_scratch(map_oh, IOD_TID_UNKNOWN, &sp, NULL, NULL) < 0)
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set scratch pad");
 
-        /* Store Metadata in scratch pad */
+        /* Open Metadata KV object for write */
         if (iod_obj_open_write(coh, mdkv_id, NULL, &mdkv_oh, NULL) < 0)
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't create scratch pad");
 
-        /* insert link count metadata on object */
-        if(NULL == (kv.value = malloc (sizeof(uint64_t))))
-            HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate buffer");
-        /* initial count is 1, since object is created now */
-        count = 1;
-        memcpy(kv.value, &count, sizeof(uint64_t));
-        kv.key = strdup("link_count");
-        if (iod_kv_set(mdkv_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-        free(kv.key);
-        free(kv.value);
+        /* insert link count metadata */
+        if(H5VL_iod_insert_link_count(mdkv_oh, IOD_TID_UNKNOWN, (uint64_t)1, 
+                                      NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* insert object type metadata */
+        if(H5VL_iod_insert_object_type(mdkv_oh, IOD_TID_UNKNOWN, H5I_MAP, 
+                                       NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
+
+        /* MSC - insert Key datatype metadata */
+        /* MSC - insert Value datatype metadata */
 
+        /* close MD KV object */
         if(iod_obj_close(mdkv_oh, NULL, NULL))
             HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't close object");
 
-        /* insert new map in kv store of parent object */
-        kv.key = strdup(last_comp);
-        kv.value = &map_id;
-        kv.value_len = sizeof(iod_obj_id_t);
-        if (iod_kv_set(cur_oh, IOD_TID_UNKNOWN, NULL, &kv, NULL, NULL) < 0)
-            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
-        free(kv.key);
+        /* add link in parent group to current object */
+        if(H5VL_iod_insert_new_link(cur_oh, IOD_TID_UNKNOWN, last_comp, map_id, 
+                                    NULL, NULL, NULL) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't insert KV value");
     } /* end if */
 
     /* close parent group if it is not the location we started the
@@ -245,13 +242,11 @@ H5VL_iod_server_map_open_cb(AXE_engine_t UNUSED axe_engine,
     if (iod_obj_open_write(coh, sp.mdkv_id, NULL /*hints*/, &mdkv_oh, NULL) < 0)
         HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "can't open scratch pad");
 
-    /* MSC - retrieve metadata */
+    /* MSC - retrieve metadata - need IOD*/
 #if 0
-    kv_size = sizeof(uint64_t);
-    /* read the map's link count */
-    if(iod_kv_get_value(mdkv_oh, IOD_TID_UNKNOWN, "link_count", output.link_count, 
-                        &kv_size, NULL, NULL) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "link_count lookup failed");
+    if(H5VL_iod_get_metadata(mdkv_oh, IOD_TID_UNKNOWN, H5VL_IOD_LINK_COUNT, "link_count",
+                             NULL, NULL, NULL, &output.link_count) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "failed to retrieve link count");
 #endif
 
     /* close the metadata scratch pad */
diff --git a/src/H5VLiod_obj.c b/src/H5VLiod_obj.c
index b9d3fda..ad64a75 100644
--- a/src/H5VLiod_obj.c
+++ b/src/H5VLiod_obj.c
@@ -85,7 +85,7 @@ H5VL_iod_server_object_open_cb(AXE_engine_t UNUSED axe_engine,
     if (iod_obj_open_write(coh, obj_id, NULL, &obj_oh, NULL) < 0)
         HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't open current group");
 
-    /* get scratch pad of the dataset */
+    /* get scratch pad of the object */
     if(iod_obj_get_scratch(cur_oh, IOD_TID_UNKNOWN, &sp, NULL, NULL) < 0)
         HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "can't get scratch pad for object");
 
diff --git a/src/H5VLiod_server.c b/src/H5VLiod_server.c
index 59c4a56..9634982 100644
--- a/src/H5VLiod_server.c
+++ b/src/H5VLiod_server.c
@@ -2934,6 +2934,321 @@ done:
     FUNC_LEAVE_NOAPI(ret_value)
 }
 
+herr_t 
+H5VL_iod_insert_plist(iod_handle_t oh, iod_trans_id_t tid, hid_t plist_id,
+                      iod_hint_list_t *hints, iod_checksum_t *cs, iod_event_t *event)
+{
+    void *key = NULL;
+    void *value = NULL;
+    iod_kv_t kv;
+    size_t buf_size;
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    /* insert group creation properties in Metadata KV */
+    key = strdup("create_plist");
+
+    /* determine the buffer size needed to store the encoded plist */ 
+    if(H5Pencode(plist_id,  NULL, &buf_size) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode plist");
+    if(NULL == (value = malloc (buf_size)))
+        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate plist buffer");
+    /* encode plist */ 
+    if(H5Pencode(plist_id, value, &buf_size) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode plist");
+
+    kv.key = (char *)key;
+    kv.value = value;
+    kv.value_len = (iod_size_t)buf_size;
+    /* insert kv pair into scratch pad */
+    if (iod_kv_set(oh, tid, hints, &kv, cs, event) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
+
+done:
+    if(key) {
+        free(key); 
+        key = NULL;
+    }
+    if(value) {
+        free(value); 
+        value = NULL;
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+}
+
+herr_t 
+H5VL_iod_insert_link_count(iod_handle_t oh, iod_trans_id_t tid, uint64_t count,
+                           iod_hint_list_t *hints, iod_checksum_t *cs, iod_event_t *event)
+{
+    void *key = NULL;
+    void *value = NULL;
+    iod_kv_t kv;
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    key = strdup("link_count");
+    if(NULL == (value = malloc (sizeof(uint64_t))))
+        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate buffer");
+
+    *((uint64_t *)value) = count;
+    kv.key = (char *)key;
+    kv.value = value;
+    kv.value_len = sizeof(uint64_t);
+
+    if (iod_kv_set(oh, tid, hints, &kv, cs, event) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
+
+done:
+    if(key) {
+        free(key); 
+        key = NULL;
+    }
+    if(value) {
+        free(value); 
+        value = NULL;
+    }
+    FUNC_LEAVE_NOAPI(ret_value)
+}
+
+herr_t 
+H5VL_iod_insert_object_type(iod_handle_t oh, iod_trans_id_t tid, H5I_type_t obj_type,
+                            iod_hint_list_t *hints, iod_checksum_t *cs, iod_event_t *event)
+{
+    void *key = NULL;
+    void *value = NULL;
+    iod_kv_t kv;
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    key = strdup("object_type");
+
+    if(NULL == (value = malloc (sizeof(int32_t))))
+        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate buffer");
+
+    *((int32_t *)value) = obj_type;
+    kv.key = (char *)key;
+    kv.value = value;
+    kv.value_len = sizeof(int32_t);
+
+    if (iod_kv_set(oh, tid, hints, &kv, cs, event) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
+
+done:
+    if(key) {
+        free(key); 
+        key = NULL;
+    }
+    if(value) {
+        free(value); 
+        value = NULL;
+    }
+    FUNC_LEAVE_NOAPI(ret_value)
+}
+
+herr_t 
+H5VL_iod_insert_new_link(iod_handle_t oh, iod_trans_id_t tid, char *link_name,
+                         iod_obj_id_t obj_id, iod_hint_list_t *hints, 
+                         iod_checksum_t *cs, iod_event_t *event)
+{
+    void *value = NULL;
+    iod_kv_t kv;
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    if(NULL == (value = malloc (sizeof(iod_obj_id_t))))
+        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate buffer");
+
+    *((int32_t *)value) = obj_id;
+    kv.key = link_name;
+    kv.value = value;
+    kv.value_len = sizeof(iod_obj_id_t);
+
+    if (iod_kv_set(oh, tid, hints, &kv, cs, event) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
+
+done:
+    if(value) {
+        free(value); 
+        value = NULL;
+    }
+    FUNC_LEAVE_NOAPI(ret_value)
+}
+
+herr_t 
+H5VL_iod_insert_datatype(iod_handle_t oh, iod_trans_id_t tid, hid_t type_id,
+                         iod_hint_list_t *hints, iod_checksum_t *cs, iod_event_t *event)
+{
+    void *key = NULL;
+    void *value = NULL;
+    iod_kv_t kv;
+    size_t buf_size;
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    /* insert group creation properties in Metadata KV */
+    key = strdup("datatype");
+
+    /* determine the buffer size needed to store the encoded type */ 
+    if(H5Tencode(type_id,  NULL, &buf_size) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode type");
+    if(NULL == (value = malloc (buf_size)))
+        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate type buffer");
+    /* encode type */ 
+    if(H5Tencode(type_id, value, &buf_size) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode type");
+
+    kv.key = (char *)key;
+    kv.value = value;
+    kv.value_len = (iod_size_t)buf_size;
+    /* insert kv pair into scratch pad */
+    if (iod_kv_set(oh, tid, hints, &kv, cs, event) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
+
+done:
+    if(key) {
+        free(key); 
+        key = NULL;
+    }
+    if(value) {
+        free(value); 
+        value = NULL;
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+}
+
+herr_t 
+H5VL_iod_insert_dataspace(iod_handle_t oh, iod_trans_id_t tid, hid_t space_id,
+                         iod_hint_list_t *hints, iod_checksum_t *cs, iod_event_t *event)
+{
+    void *key = NULL;
+    void *value = NULL;
+    iod_kv_t kv;
+    size_t buf_size;
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    /* insert group creation properties in Metadata KV */
+    key = strdup("dataspace");
+
+    /* determine the buffer size needed to store the encoded space */ 
+    if(H5Sencode(space_id,  NULL, &buf_size) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode space");
+    if(NULL == (value = malloc (buf_size)))
+        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate space buffer");
+    /* encode space */ 
+    if(H5Sencode(space_id, value, &buf_size) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTENCODE, FAIL, "failed to encode space");
+
+    kv.key = (char *)key;
+    kv.value = value;
+    kv.value_len = (iod_size_t)buf_size;
+    /* insert kv pair into scratch pad */
+    if (iod_kv_set(oh, tid, hints, &kv, cs, event) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't set KV pair in parent");
+
+done:
+    if(key) {
+        free(key); 
+        key = NULL;
+    }
+    if(value) {
+        free(value); 
+        value = NULL;
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+}
+
+herr_t 
+H5VL_iod_get_metadata(iod_handle_t oh, iod_trans_id_t tid, H5VL_iod_metadata_t md_type,
+                      const char *key, iod_hint_list_t *hints, iod_checksum_t *cs, 
+                      iod_event_t *event, void *ret)
+{
+    iod_size_t val_size = 0;
+    void *value;
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    switch(md_type) {
+    case H5VL_IOD_PLIST:
+        {
+            hid_t plist_id = *((hid_t *)ret);
+
+            if(iod_kv_get_value(oh, tid, key, NULL, &val_size, cs, event) < 0)
+                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "lookup failed");
+
+            if(NULL == (value = malloc (val_size)))
+                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate value buffer");
+
+            if(iod_kv_get_value(oh, tid, key, value, &val_size, hints, event) < 0)
+                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "lookup failed");
+
+            if((plist_id = H5Pdecode(value)) < 0)
+                HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode gcpl");
+            break;
+        }
+    case H5VL_IOD_LINK_COUNT:
+        val_size = sizeof(uint64_t);
+        if(iod_kv_get_value(oh, tid, key, ret, &val_size, cs, event) < 0)
+            HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "link_count lookup failed");
+        break;
+    case H5VL_IOD_DATATYPE:
+        {
+            hid_t type_id = *((hid_t *)ret);
+
+            if(iod_kv_get_value(oh, tid, key, NULL, &val_size, cs, event) < 0)
+                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "lookup failed");
+
+            if(NULL == (value = malloc (val_size)))
+                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate value buffer");
+
+            if(iod_kv_get_value(oh, tid, key, value, &val_size, hints, event) < 0)
+                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "lookup failed");
+
+            if((type_id = H5Tdecode(value)) < 0)
+                HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode gcpl");
+            break;
+        }
+    case H5VL_IOD_DATASPACE:
+        {
+            hid_t space_id = *((hid_t *)ret);
+
+            if(iod_kv_get_value(oh, tid, key, NULL, &val_size, cs, event) < 0)
+                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "lookup failed");
+
+            if(NULL == (value = malloc (val_size)))
+                HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't allocate value buffer");
+
+            if(iod_kv_get_value(oh, tid, key, value, &val_size, hints, event) < 0)
+                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "lookup failed");
+
+            if((space_id = H5Tdecode(value)) < 0)
+                HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "failed to decode gcpl");
+            break;
+        }
+    default:
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "invalide metadata type");
+    }
+done:
+    if(value) {
+        free(value); 
+        value = NULL;
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+}
+
+
+
 #if 0
 
 /*-------------------------------------------------------------------------
diff --git a/src/H5VLiod_server.h b/src/H5VLiod_server.h
index deda473..f483d25 100644
--- a/src/H5VLiod_server.h
+++ b/src/H5VLiod_server.h
@@ -30,6 +30,15 @@
 #define EEXISTS 1
 #define H5_DO_NATIVE 0
 
+/* Enum for metadata types stored in MD KV for HDF5->IOD objects */
+typedef enum H5VL_iod_metadata_t {
+    H5VL_IOD_PLIST,             /*type ID for property lists     	    */
+    H5VL_IOD_LINK_COUNT,        /*type ID for link count                    */
+    H5VL_IOD_OBJECT_TYPE,       /*type ID for object type                   */
+    H5VL_IOD_DATATYPE,          /*type ID for datatypes                     */
+    H5VL_IOD_DATASPACE          /*type ID for dataspaces                    */
+} H5VL_iod_metadata_t;
+
 /* the AXE op data strucutre stored with every operation */
 typedef struct op_data_t {
     void *input;
@@ -257,10 +266,26 @@ H5_DLL void H5VL_iod_server_object_get_comment_cb(AXE_engine_t UNUSED axe_engine
                                                   size_t num_s_parents, AXE_task_t s_parents[], 
                                                   void *_op_data);
 
+/* Helper routines used several times in different places */
 H5_DLL herr_t H5VL_iod_server_traverse(iod_handle_t coh, iod_obj_id_t loc_id, iod_handle_t loc_handle, 
                                        const char *path, hbool_t create_interm_grps,
                                        char **last_comp, iod_obj_id_t *iod_id, iod_handle_t *iod_oh);
 H5_DLL herr_t H5VL_iod_get_file_desc(hid_t space_id, hssize_t *count, iod_hyperslab_t *hslabs);
-
+H5_DLL herr_t H5VL_iod_insert_plist(iod_handle_t oh, iod_trans_id_t tid, hid_t plist_id,
+                                    iod_hint_list_t *hints, iod_checksum_t *cs, iod_event_t *event);
+H5_DLL herr_t H5VL_iod_insert_link_count(iod_handle_t oh, iod_trans_id_t tid, uint64_t count,
+                                         iod_hint_list_t *hints, iod_checksum_t *cs, iod_event_t *event);
+H5_DLL herr_t H5VL_iod_insert_object_type(iod_handle_t oh, iod_trans_id_t tid, H5I_type_t obj_type,
+                                          iod_hint_list_t *hints, iod_checksum_t *cs, iod_event_t *event);
+H5_DLL herr_t H5VL_iod_insert_datatype(iod_handle_t oh, iod_trans_id_t tid, hid_t type_id,
+                                       iod_hint_list_t *hints, iod_checksum_t *cs, iod_event_t *event);
+H5_DLL herr_t H5VL_iod_insert_dataspace(iod_handle_t oh, iod_trans_id_t tid, hid_t space_id,
+                                        iod_hint_list_t *hints, iod_checksum_t *cs, iod_event_t *event);
+H5_DLL herr_t H5VL_iod_insert_new_link(iod_handle_t oh, iod_trans_id_t tid, char *link_name,
+                                       iod_obj_id_t obj_id, iod_hint_list_t *hints, 
+                                       iod_checksum_t *cs, iod_event_t *event);
+H5_DLL herr_t H5VL_iod_get_metadata(iod_handle_t oh, iod_trans_id_t tid, H5VL_iod_metadata_t md_type,
+                                    const char *key, iod_hint_list_t *hints, iod_checksum_t *cs, 
+                                    iod_event_t *event, void *ret);
 #endif /* H5_HAVE_EFF */
 #endif /* _H5VLiod_server_H */