Stash work on object header reduction code and tests.

CMake stuff is not verified.

18 files changed, 1101 insertions, 101 deletions

diff --git a/MANIFEST b/MANIFEST
index 1165240..68763aa 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -1041,6 +1041,7 @@
 ./test/none.h5
 ./test/ntypes.c
 ./test/ohdr.c
+./test/ohdr_min.c
 ./test/objcopy.c
 ./test/page_buffer.c
 ./test/paged_nopersist.h5
diff --git a/src/H5Dint.c b/src/H5Dint.c
index e8874a2..6d095aa 100644
--- a/src/H5Dint.c
+++ b/src/H5Dint.c
@@ -61,7 +61,9 @@ static herr_t H5D__init_storage(const H5D_io_info_t *io_info, hbool_t full_overw
 static herr_t H5D__get_storage_size_real(const H5D_t *dset, hsize_t *storage_size);
 static herr_t H5D__append_flush_setup(H5D_t *dset, hid_t dapl_id);
 static herr_t H5D__close_cb(H5D_t *dataset);
-
+static herr_t H5D__use_minimized_dset_headers(H5F_t *file, H5D_t *dset, hbool_t *minimize);
+static herr_t H5D__prepare_minimized_oh(H5F_t *file, H5D_t *dset, H5O_loc_t *oloc);
+static size_t H5D__calculate_minimum_header_size(H5F_t *file, H5D_t *dset, H5O_t *ohdr);
 /*********************/
 /* Package Variables */
 /*********************/
@@ -662,6 +664,272 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:   H5D__use_minimized_dset_headers
+ *
+ * Purpose:    Compartmentalize check for file- or dcpl-set values indicating
+ *             to create a "minimized" dataset object header.
+ *             Upon success, write resulting value to out pointer `minimize`.
+ *
+ * Return:     Success: SUCCEED (0) (non-negative value)
+ *             Failure: FAIL (-1) (negative value)
+ *
+ * Programmer: Jacob Smith
+ *             16 August 2018
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5D__use_minimized_dset_headers( \
+        H5F_t   *file,           \
+        H5D_t   *dset,           \
+        hbool_t *minimize)
+{
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT;
+
+    HDassert(file);
+    HDassert(dset);
+    HDassert(minimize);
+
+    if (FAIL == H5Pget_dset_no_attrs_hint(dset->shared->dcpl_id, minimize))
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL,
+                    "can't get minimize value from dcpl")
+
+#if 1 /* TODO: problem getting file id? */
+    /* error kicks in when tring to create dset through external link */
+    if (FALSE == *minimize) {
+#if 1 /* API or direct */
+        /* problems getting/verifying object id */
+        hid_t file_id = -1;
+        file_id = H5F_get_file_id((const H5F_t *)file);
+        if (0 > file_id)
+            HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL,
+                        "can't get file id")
+
+#if 1 /* which file-id verification */
+        if (NULL == H5I_object(file_id))
+            HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL,
+                        "file id seems to be invalid")
+#else
+        if (NULL == H5I_object_verify(file_id, H5I_FILE))
+            HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL,
+                        "file id seems to be invalid")
+#endif /* which file-id verification */
+
+        if (FAIL == H5Fget_dset_no_attrs_hint(file_id, minimize))
+            HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL,
+                        "can't get minimize value from file")
+#else
+        /* direct access -- "incomplete type" */
+        HDassert(file->shared);
+        minimize = file->shared->crt_dset_min_ohdr_flag;
+#endif /* API or direct */
+    } /* if to look in file for flag */
+#endif /* TODO */
+
+done:
+    if (FAIL == ret_value)
+        *minimize = FALSE;
+    FUNC_LEAVE_NOAPI(ret_value);
+} /* H5D__use_minimized_dset_headers */
+
+
+/*-------------------------------------------------------------------------
+ * Function:   H5D__calculate_minimium_header_size
+ *
+ * Purpose:    Calculate the size required for the minimized object header.
+ *
+ * Return:     Success: SUCCEED (0) (non-negative value)
+ *             Failure: FAIL (-1) (negative value)
+ *
+ * Programmer: Jacob Smith
+ *             16 August 2018
+ *-------------------------------------------------------------------------
+ */
+static size_t
+H5D__calculate_minimum_header_size( \
+        H5F_t *file,                \
+        H5D_t *dset,                \
+        H5O_t *ohdr)
+{
+    H5T_t      *type             = NULL;
+    H5O_fill_t *fill_prop        = NULL;
+    hbool_t     use_at_least_v18 = FALSE;
+    size_t      ret_value        = 0;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR;
+
+    HDassert(file);
+    HDassert(dset);
+    HDassert(ohdr);
+
+    type = dset->shared->type;
+    fill_prop = &(dset->shared->dcpl_cache.fill);
+    use_at_least_v18 = (H5F_LOW_BOUND(file) >= H5F_LIBVER_V18);
+
+    /* Datatype message size */
+    ret_value += H5O_msg_size_oh(
+            file,
+            ohdr,
+            H5O_DTYPE_ID,
+            type,
+            0);
+
+    /* Shared Dataspace message size */
+    ret_value += H5O_msg_size_oh(
+            file,
+            ohdr,
+            H5O_SDSPACE_ID,
+            dset->shared->space,
+            0);
+
+    /* "Layout" message size */
+    ret_value += H5O_msg_size_oh(
+            file,
+            ohdr,
+            H5O_LAYOUT_ID,
+            &dset->shared->layout,
+            0);
+
+    /* Fill Value message size */
+    ret_value += H5O_msg_size_oh(
+            file,
+            ohdr,
+            H5O_FILL_NEW_ID,
+            fill_prop,
+            0);
+
+#if 1 /* DEBUG H5Omessage */
+    /* "Continuation" message size */
+#if 0
+    ret_value += H5O_msg_raw_size(
+            file,
+            H5O_CONT_ID,
+            FALSE,
+            NULL);
+#else
+    {
+    char tmp[1] = "\0";
+    ret_value += H5O_msg_size_oh(
+            file,
+            ohdr,
+            H5O_CONT_ID,
+            tmp, /* NULL, */ /* UNUSED? */ /*intercepted by assert before passed through */
+            0);
+    }
+#endif
+#endif /* DEBUG H5Omessage */
+
+    /* Fill Value (backwards compatability) message size */
+    if (fill_prop->buf && !use_at_least_v18) {
+        H5O_fill_t old_fill_prop; /* Copy for writing "old" fill value */
+
+        /* Shallow copy the fill value property */
+        /* guards against shared component modification */
+        HDmemcpy(&old_fill_prop, fill_prop, sizeof(old_fill_prop));
+
+        H5O_msg_reset_share(H5O_FILL_ID, &old_fill_prop);
+
+        ret_value += H5O_msg_size_oh(
+                file,
+                ohdr,
+                H5O_FILL_ID,
+                &old_fill_prop,
+                0);
+    }
+
+    /* Filter/Pipeline message size */
+    if (H5D_CHUNKED == dset->shared->layout.type) {
+        H5O_pline_t *pline = &dset->shared->dcpl_cache.pline;
+        if (pline->nused > 0) {
+            ret_value += H5O_msg_size_oh(
+                    file,
+                    ohdr,
+                    H5O_PLINE_ID,
+                    pline,
+                    0);
+        }
+    }
+
+    /* External File Link message size */
+    if (dset->shared->dcpl_cache.efl.nused > 0) {
+        ret_value += H5O_msg_size_oh(
+                file,
+                ohdr,
+                H5O_EFL_ID,
+                &dset->shared->dcpl_cache.efl,
+                0);
+    }
+
+    /* Modification Time message size */
+    if ((H5O_OH_GET_VERSION(ohdr) > 1) && /* TODO: H5O_VERSION_1 in H5Opkg.h */
+        (H5O_HDR_STORE_TIMES & H5O_OH_GET_FLAGS(ohdr)))
+    {
+        time_t mtime = H5O_OH_GET_MTIME(ohdr);
+        ret_value += H5O_msg_size_oh(
+                file,
+                ohdr,
+                H5O_MTIME_NEW_ID,
+                &mtime,
+                0);
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value);
+} /* H5D__calculate_minimum_header_size */
+
+
+/*-------------------------------------------------------------------------
+ * Function:   H5D__prepare_minimized_oh
+ *
+ * Purpose:    Create an object header (H5O_t) allocated with the smallest
+ *             possible size.
+ *
+ * Return:     Success: SUCCEED (0) (non-negative value)
+ *             Failure: FAIL (-1) (negative value)
+ *
+ * Programmer: Jacob Smith
+ *             16 August 2018
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5D__prepare_minimized_oh( \
+        H5F_t     *file,   \
+        H5D_t     *dset,   \
+        H5O_loc_t *oloc)
+{
+    H5O_t  *oh        = NULL;
+    size_t  ohdr_size = 0;
+    herr_t  ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT;
+
+    HDassert(file);
+    HDassert(dset);
+    HDassert(oloc);
+
+    oh = H5O__create_ohdr(file, dset->shared->dcpl_id);
+    if (NULL == oh)
+        HGOTO_ERROR(H5E_OHDR, H5E_BADVALUE, FAIL,
+                    "can't instantiate object header")
+
+    ohdr_size = H5D__calculate_minimum_header_size(file, dset, oh);
+
+    if (FAIL == H5O__apply_ohdr(
+            file,
+            oh,
+            dset->shared->dcpl_id,
+            ohdr_size,
+            (size_t)1,
+            oloc))
+        HGOTO_ERROR(H5E_OHDR, H5E_BADVALUE, FAIL,
+                    "can't apply object header to file")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+} /* H5D_prepare_minimized_oh */
+
+
+/*-------------------------------------------------------------------------
  * Function: H5D__update_oh_info
  *
  * Purpose:  Create and fill object header for dataset
@@ -683,6 +951,7 @@ H5D__update_oh_info(H5F_t *file, H5D_t *dset, hid_t dapl_id)
     hbool_t             fill_changed = FALSE;   /* Flag indicating the fill value was changed */
     hbool_t             layout_init = FALSE;    /* Flag to indicate that chunk information was initialized */
     hbool_t             use_at_least_v18;       /* Flag indicating to use at least v18 format versions */
+    hbool_t             minimize_header = FALSE;
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_STATIC
@@ -751,19 +1020,42 @@ H5D__update_oh_info(H5F_t *file, H5D_t *dset, hid_t dapl_id)
             HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set fill value info")
     } /* end if */
 
-    /* Add the dataset's raw data size to the size of the header, if the raw data will be stored as compact */
-    if(layout->type == H5D_COMPACT)
-        ohdr_size += layout->storage.u.compact.size;
+    if (FAIL == H5D__use_minimized_dset_headers(file, dset, &minimize_header))
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTGET, FAIL,
+                    "can't get minimize settings")
+    if (TRUE == minimize_header) {
+        if (FAIL == H5D__prepare_minimized_oh(file, dset, oloc))
+            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL,
+                        "can't create minimized dataset object header")
+    } else {
+        /* Add the dataset's raw data size to the size of the header, if the
+         * raw data will be stored as compact
+         */
+        if (H5D_COMPACT == layout->type)
+            ohdr_size += layout->storage.u.compact.size;
+
+        /* Create an object header for the dataset */
+        if (0 > H5O_create(
+                file,
+                ohdr_size,
+                (size_t)1,
+                dset->shared->dcpl_id,
+                oloc/*out*/))
+            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL,
+                        "unable to create dataset object header")
+    } /* If use minimum/standard object header space */
 
-    /* Create an object header for the dataset */
-    if(H5O_create(file, ohdr_size, (size_t)1, dset->shared->dcpl_id, oloc/*out*/) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to create dataset object header")
     HDassert(file == dset->oloc.file);
 
     /* Pin the object header */
     if(NULL == (oh = H5O_pin(oloc)))
         HGOTO_ERROR(H5E_DATASET, H5E_CANTPIN, FAIL, "unable to pin dataset object header")
 
+#if 0
+       HDprintf("DATATYPE SIZE: %lu\n",
+               H5O_msg_size_oh(file, oh, H5O_DTYPE_ID, type, 0));
+#endif /* TESTING DEBUG */
+
     /* Write the dataspace header message */
     if(H5S_append(file, oh, dset->shared->space) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to update dataspace header message")
diff --git a/src/H5Dprivate.h b/src/H5Dprivate.h
index cbee0de..e136c80 100644
--- a/src/H5Dprivate.h
+++ b/src/H5Dprivate.h
@@ -45,6 +45,7 @@
 #define H5D_CRT_FILL_VALUE_NAME    "fill_value"          /* Fill value */
 #define H5D_CRT_ALLOC_TIME_STATE_NAME "alloc_time_state" /* Space allocation time state */
 #define H5D_CRT_EXT_FILE_LIST_NAME "efl"                 /* External file list */
+#define H5D_CRT_MIN_DSET_HDR_SIZE_NAME "dset_oh_minimize"/* Minimize object header */
 
 /* ========  Dataset access property names ======== */
 #define H5D_ACS_DATA_CACHE_NUM_SLOTS_NAME   "rdcc_nslots"    /* Size of raw data chunk cache(slots) */
diff --git a/src/H5F.c b/src/H5F.c
index 01fd7db..7e206bb 100644
--- a/src/H5F.c
+++ b/src/H5F.c
@@ -1713,3 +1713,97 @@ H5Fincrement_filesize(hid_t file_id, hsize_t increment)
 done:
     FUNC_LEAVE_API(ret_value)
 } /* H5Fincrement_filesize() */
+
+
+/*-------------------------------------------------------------------------
+ * Function: H5Fget_dset_no_attrs_hint
+ *
+ * Purpose:
+ *
+ *     Get the file-level setting to create minimized dataset object headers.
+ *     Result is stored at pointer `minimize`.
+ *
+ * Return:
+ *
+ *     Success: SUCCEED (0) (non-negative value)
+ *     Failure: FAIL (-1) (negative value)
+ *
+ * Programmer:
+ *
+ *     Jacob Smith
+ *     15 August 2018
+ *
+ * Changes: None.
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Fget_dset_no_attrs_hint(hid_t    file_id,
+                          hbool_t *minimize)
+{
+    H5F_t  *f         = NULL;
+    herr_t  ret_value = SUCCEED;
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*b", file_id, minimize);
+
+    if (NULL == minimize)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, 
+                    "out pointer 'minimize' cannot be NULL")
+
+    f = (H5F_t *)H5I_object_verify(file_id, H5I_FILE);
+    if (NULL == f)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, 
+                    "can't get file from id")
+
+    HDassert(f->shared);
+
+    *minimize = f->shared->crt_dset_min_ohdr_flag;
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* H5Fget_dset_no_attrs_hint */
+
+
+/*-------------------------------------------------------------------------
+ * Function: H5Fset_dset_no_attrs_hint
+ *
+ * Purpose:
+ *
+ *     Set the file-level setting to create minimized dataset object headers.
+ *
+ * Return:
+ *
+ *     Success: SUCCEED (0) (non-negative value)
+ *     Failure: FAIL (-1) (negative value)
+ *
+ * Programmer:
+ *
+ *     Jacob Smith
+ *     15 August 2018
+ *
+ * Changes: None.
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Fset_dset_no_attrs_hint(hid_t   file_id,   
+                          hbool_t minimize)
+{
+    H5F_t  *f         = NULL;
+    herr_t  ret_value = SUCCEED;
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "ib", file_id, minimize);
+
+    f = (H5F_t *)H5I_object_verify(file_id, H5I_FILE);
+    if (NULL == f)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "can't get file from id")
+
+    HDassert(f->shared);
+
+    f->shared->crt_dset_min_ohdr_flag = minimize;
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* H5Fset_dset_no_attrs_hint */
+
diff --git a/src/H5Fint.c b/src/H5Fint.c
index abc638a..c3fe07a 100644
--- a/src/H5Fint.c
+++ b/src/H5Fint.c
@@ -880,6 +880,9 @@ H5F__new(H5F_file_t *shared, unsigned flags, hid_t fcpl_id, hid_t fapl_id, H5FD_
         /* intialize point of no return */
         f->shared->point_of_no_return = FALSE;
 
+        /* set default value for minimizing dataset object headers */
+        f->shared->crt_dset_min_ohdr_flag = FALSE;
+
         /* Copy the file creation and file access property lists into the
          * new file handle. We do this early because some values might need
          * to change as the file is being opened.
diff --git a/src/H5Fpkg.h b/src/H5Fpkg.h
index 2ab41de..edbd460 100644
--- a/src/H5Fpkg.h
+++ b/src/H5Fpkg.h
@@ -353,6 +353,7 @@ struct H5F_file_t {
 
     /* Object flush info */
     H5F_object_flush_t 	object_flush;	    /* Information for object flush callback */
+    hbool_t crt_dset_min_ohdr_flag; /* flag to minimize created dataset object header */
 };
 
 /*
diff --git a/src/H5Fpublic.h b/src/H5Fpublic.h
index 73c59f5..6274eb0 100644
--- a/src/H5Fpublic.h
+++ b/src/H5Fpublic.h
@@ -273,6 +273,8 @@ H5_DLL herr_t H5Freset_page_buffering_stats(hid_t file_id);
 H5_DLL herr_t H5Fget_page_buffering_stats(hid_t file_id, unsigned accesses[2],
     unsigned hits[2], unsigned misses[2], unsigned evictions[2], unsigned bypasses[2]);
 H5_DLL herr_t H5Fget_mdc_image_info(hid_t file_id, haddr_t *image_addr, hsize_t *image_size);
+H5_DLL herr_t H5Fget_dset_no_attrs_hint(hid_t file_id, hbool_t *minimize);
+H5_DLL herr_t H5Fset_dset_no_attrs_hint(hid_t file_id, hbool_t minimize);
 
 #ifdef H5_HAVE_PARALLEL
 H5_DLL herr_t H5Fset_mpi_atomicity(hid_t file_id, hbool_t flag);
diff --git a/src/H5Oint.c b/src/H5Oint.c
index 2752a25..1d07415 100644
--- a/src/H5Oint.c
+++ b/src/H5Oint.c
@@ -83,7 +83,6 @@ static herr_t H5O__visit_cb(hid_t group, const char *name, const H5L_info_t *lin
     void *_udata);
 static const H5O_obj_class_t *H5O__obj_class_real(const H5O_t *oh);
 
-
 /*********************/
 /* Package Variables */
 /*********************/
@@ -277,130 +276,276 @@ done:
  *		matzke@llnl.gov
  *		Aug  5 1997
  *
+ * Changes:     17 August 2018
+ *              Jacob Smith 
+ *              Refactor out the operations into two separate steps --
+ *              preparation and application -- to facilitate overriding the
+ *              library-default size allocated for the object header. This
+ *              function is retained as a wrapper, to minimize changes to
+ *              unaffected calling functions.
+ *
  *-------------------------------------------------------------------------
  */
 herr_t
-H5O_create(H5F_t *f, size_t size_hint, size_t initial_rc, hid_t ocpl_id,
-    H5O_loc_t *loc/*out*/)
+H5O_create(                \
+        H5F_t *f,          \
+        size_t size_hint,  \
+        size_t initial_rc, \
+        hid_t ocpl_id,     \
+        H5O_loc_t *loc) /*out*/
 {
-    H5P_genplist_t  *oc_plist;          /* Object creation property list */
-    H5O_t      *oh = NULL;              /* Object header created */
-    haddr_t     oh_addr;                /* Address of initial object header */
-    size_t      oh_size;                /* Size of initial object header */
-    uint8_t	oh_flags;		/* Object header's initial status flags */
-    unsigned    insert_flags = H5AC__NO_FLAGS_SET; /* Flags for inserting object header into cache */
-    hbool_t     store_msg_crt_idx;      /* Whether to always store message creation indices for this file */
-    herr_t      ret_value = SUCCEED;    /* return value */
+    H5O_t  *oh        = NULL;
+    herr_t  ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI(FAIL)
 
-    /* check args */
     HDassert(f);
     HDassert(loc);
     HDassert(TRUE == H5P_isa_class(ocpl_id, H5P_OBJECT_CREATE));
 
+    /* create object header in freelist
+     * header version is set internally
+     */
+    oh = H5O__create_ohdr(f, ocpl_id);
+    if (NULL == oh)
+        HGOTO_ERROR(H5E_OHDR, H5E_BADVALUE, FAIL,
+                    "Can't instantiate object header")
+
+    /* apply object header information to file
+     */
+    if (0 > H5O__apply_ohdr(
+            f,
+            oh,
+            ocpl_id,
+            size_hint,
+            initial_rc,
+            loc))
+    {
+        HGOTO_ERROR(H5E_OHDR, H5E_BADVALUE, FAIL,
+                    "Can't apply object header to file")
+    }
+
+done:
+    if (FAIL == ret_value &&
+        NULL != oh        &&
+        0 > H5O__free(oh))
+    {
+        HDONE_ERROR(H5E_OHDR, H5E_CANTFREE, FAIL,
+                    "can't delete object header")
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5O_create() */
+
+
+/*-----------------------------------------------------------------------------
+ * Function:   H5O__create_ohdr
+ *
+ * Purpose:    Create the object header, set version and flags.
+ *
+ * Return:     Success: Pointer to the newly-crated header object.
+ *             Failure: NULL
+ *
+ * Programmer: Jacob Smith
+ *             17 August 2018
+ *
+ *-----------------------------------------------------------------------------
+ */
+H5O_t *
+H5O__create_ohdr(     \
+        H5F_t *f,     \
+        hid_t  ocpl_id)
+{
+    H5P_genplist_t *oc_plist;
+    H5O_t          *oh = NULL;        /* Object header in Freelist */
+    uint8_t         oh_flags;         /* Initial status flags */
+    H5O_t          *ret_value = NULL;
+
+    FUNC_ENTER_NOAPI(NULL)
+
+    HDassert(f);
+    HDassert(TRUE == H5P_isa_class(ocpl_id, H5P_OBJECT_CREATE));
+
     /* Check for invalid access request */
-    if(0 == (H5F_INTENT(f) & H5F_ACC_RDWR))
-        HGOTO_ERROR(H5E_OHDR, H5E_BADVALUE, FAIL, "no write intent on file")
+    if (0 == (H5F_INTENT(f) & H5F_ACC_RDWR))
+        HGOTO_ERROR(H5E_OHDR, H5E_BADVALUE, NULL,
+                    "no write intent on file")
 
-    /* Make certain we allocate at least a reasonable size for the object header */
-    size_hint = H5O_ALIGN_F(f, MAX(H5O_MIN_SIZE, size_hint));
+    oh = H5FL_CALLOC(H5O_t);
+    if (NULL == oh)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL,
+                    "memory allocation failed")
 
-    /* Get the property list */
-    if(NULL == (oc_plist = (H5P_genplist_t *)H5I_object(ocpl_id)))
-        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a property list")
+    oc_plist = (H5P_genplist_t *)H5I_object(ocpl_id);
+    if (NULL == oc_plist)
+        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, NULL,
+                    "not a property list")
 
     /* Get any object header status flags set by properties */
-    if(H5P_get(oc_plist, H5O_CRT_OHDR_FLAGS_NAME, &oh_flags) < 0)
-        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get object header flags")
+    if (0 > H5P_get(oc_plist, H5O_CRT_OHDR_FLAGS_NAME, &oh_flags))
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, NULL,
+                    "can't get object header flags")
 
-    /* Allocate the object header and zero out header fields */
-    if(NULL == (oh = H5FL_CALLOC(H5O_t)))
-        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
+    if (0 > H5O_set_version(f, oh, oh_flags, H5F_STORE_MSG_CRT_IDX(f)))
+        HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, NULL,
+                    "can't set version of object header")
 
-    /* Initialize file-specific information for object header */
-    store_msg_crt_idx = H5F_STORE_MSG_CRT_IDX(f);
+    oh->flags = oh_flags;
 
-    if(H5O_set_version(f, oh, oh_flags, store_msg_crt_idx) < 0)
-        HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set version of objecdt header")
+    ret_value = oh;
+
+done:
+    if (NULL == ret_value &&
+        NULL != oh        &&
+        0 > H5O__free(oh))
+    {
+        HDONE_ERROR(H5E_OHDR, H5E_CANTFREE, NULL,
+                    "can't delete object header")
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5O__create_ohdr */
+
+
+/*-----------------------------------------------------------------------------
+ * Function:   H5O__apply_ohdr
+ *
+ * Purpose:    Initialize and set the object header in the file.
+ *             Record some information at `loc_out`.
+ *
+ * Return:     Success: SUCCEED (0) (non-negative value)
+ *             Failure: FAI (-1) (negative value)
+ *
+ * Programmer: Jacob Smith
+ *             17 August 2018
+ *
+ *-----------------------------------------------------------------------------
+ */
+herr_t
+H5O__apply_ohdr(               \
+        H5F_t     *f,          \
+        H5O_t     *oh,         \
+        hid_t      ocpl_id,    \
+        size_t     size_hint,  \
+        size_t     initial_rc, \
+        H5O_loc_t *loc_out)
+{
+    haddr_t         oh_addr;
+    size_t          oh_size;
+    H5P_genplist_t *oc_plist     = NULL;
+    unsigned        insert_flags = H5AC__NO_FLAGS_SET;
+    herr_t          ret_value    = SUCCEED;
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    HDassert(f);
+    HDassert(loc_out);
+    HDassert(oh);
+    HDassert(TRUE == H5P_isa_class(ocpl_id, H5P_OBJECT_CREATE));
+
+    /* Allocate at least a reasonable size for the object header */
+    size_hint = H5O_ALIGN_F(f, MAX(H5O_MIN_SIZE, size_hint));
 
     oh->sizeof_size = H5F_SIZEOF_SIZE(f);
     oh->sizeof_addr = H5F_SIZEOF_ADDR(f);
-    oh->swmr_write = !!(H5F_INTENT(f) & H5F_ACC_SWMR_WRITE);
+    oh->swmr_write = !!(H5F_INTENT(f) & H5F_ACC_SWMR_WRITE); /* funky cast */
+
 #ifdef H5O_ENABLE_BAD_MESG_COUNT
-    /* Check whether the "bad message count" property is set */
-    if(H5P_exist_plist(oc_plist, H5O_BAD_MESG_COUNT_NAME) > 0) {
-        /* Retrieve bad message count flag */
-        if(H5P_get(oc_plist, H5O_BAD_MESG_COUNT_NAME, &oh->store_bad_mesg_count) < 0)
-            HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "can't get bad message count flag")
+    if (0 < H5P_exist_plist(oc_plist, H5O_BAD_MESG_COUNT_NAME)) {
+        /* Set bad message count flag -- from property list */
+        if (0 > H5P_get(oc_plist,
+                        H5O_BAD_MESG_COUNT_NAME,
+                        &oh->store_bad_mesg_count))
+        {
+            HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL,
+                        "can't get bad message count flag")
+        }
     }
 #endif /* H5O_ENABLE_BAD_MESG_COUNT */
 
     /* Create object header proxy if doing SWMR writes */
-    if(oh->swmr_write) {
-        /* Create virtual entry, for use as proxy */
-        if(NULL == (oh->proxy = H5AC_proxy_entry_create()))
-            HGOTO_ERROR(H5E_OHDR, H5E_CANTCREATE, FAIL, "can't create object header proxy")
-    }
-    else
+    if (oh->swmr_write) {
+        oh->proxy = H5AC_proxy_entry_create();
+        if (NULL == oh->proxy)
+            HGOTO_ERROR(H5E_OHDR, H5E_CANTCREATE, FAIL,
+                        "can't create object header proxy")
+    } else {
         oh->proxy = NULL;
+    }
 
-    /* Set initial status flags */
-    oh->flags = oh_flags;
+    oc_plist = (H5P_genplist_t *)H5I_object(ocpl_id);
+    if (NULL == oc_plist)
+        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL,
+                    "not a property list")
 
     /* Initialize version-specific fields */
-    if(oh->version > H5O_VERSION_1) {
-        /* Initialize all time fields with current time, if we are storing them */
-        if(oh->flags & H5O_HDR_STORE_TIMES)
+    if (oh->version > H5O_VERSION_1) {
+        /* Initialize all time fields */
+        if (oh->flags & H5O_HDR_STORE_TIMES)
             oh->atime = oh->mtime = oh->ctime = oh->btime = H5_now();
         else
             oh->atime = oh->mtime = oh->ctime = oh->btime = 0;
 
-        /* Make certain attribute creation order tracking is enabled if
-         *      attributes can be shared in this file.
-         */
-        if(store_msg_crt_idx)
+        if (H5F_STORE_MSG_CRT_IDX(f))
+            /* flag to record message creation indices */
             oh->flags |= H5O_HDR_ATTR_CRT_ORDER_TRACKED;
 
-        /* Retrieve attribute storage phase change values from property list */
-        if(H5P_get(oc_plist, H5O_CRT_ATTR_MAX_COMPACT_NAME, &oh->max_compact) < 0)
-            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get max. # of compact attributes")
-        if(H5P_get(oc_plist, H5O_CRT_ATTR_MIN_DENSE_NAME, &oh->min_dense) < 0)
-            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get min. # of dense attributes")
+        /* Set attribute storage phase change values -- from property list */
+        if (0 > H5P_get(oc_plist,
+                        H5O_CRT_ATTR_MAX_COMPACT_NAME,
+                        &oh->max_compact))
+        {
+            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL,
+                        "can't get max. # of compact attributes")
+        }
+        if (0 > H5P_get(oc_plist,
+                        H5O_CRT_ATTR_MIN_DENSE_NAME,
+                        &oh->min_dense))
+        {
+            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL,
+                        "can't get min. # of dense attributes")
+        }
 
         /* Check for non-default attribute storage phase change values */
-        if(oh->max_compact != H5O_CRT_ATTR_MAX_COMPACT_DEF || oh->min_dense != H5O_CRT_ATTR_MIN_DENSE_DEF)
+        if (H5O_CRT_ATTR_MAX_COMPACT_DEF != oh->max_compact  || \
+            H5O_CRT_ATTR_MIN_DENSE_DEF   != oh->min_dense   )
+        {
             oh->flags |= H5O_HDR_ATTR_STORE_PHASE_CHANGE;
+        }
 
         /* Determine correct value for chunk #0 size bits */
 /* Avoid compiler warning on 32-bit machines */
 #if H5_SIZEOF_SIZE_T > H5_SIZEOF_INT32_T
-        if(size_hint > 4294967295UL)
+        if (size_hint > 4294967295UL)
             oh->flags |= H5O_HDR_CHUNK0_8;
         else
 #endif /* H5_SIZEOF_SIZE_T > H5_SIZEOF_INT32_T */
-        if(size_hint > 65535)
+        if (size_hint > 65535)
             oh->flags |= H5O_HDR_CHUNK0_4;
-        else if(size_hint > 255)
+        else if (size_hint > 255)
             oh->flags |= H5O_HDR_CHUNK0_2;
-    } /* end if */
-    else {
+    } else {
         /* Reset unused time fields */
         oh->atime = oh->mtime = oh->ctime = oh->btime = 0;
-    } /* end else */
+    } /* end if/else header version >1 */
 
     /* Compute total size of initial object header */
     /* (i.e. object header prefix and first chunk) */
     oh_size = (size_t)H5O_SIZEOF_HDR(oh) + size_hint;
 
     /* Allocate disk space for header and first chunk */
-    if(HADDR_UNDEF == (oh_addr = H5MF_alloc(f, H5FD_MEM_OHDR, (hsize_t)oh_size)))
-        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "file allocation failed for object header")
+    oh_addr = H5MF_alloc(f, H5FD_MEM_OHDR, (hsize_t)oh_size);
+    if (HADDR_UNDEF == oh_addr)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
+                    "file allocation failed for object header")
 
     /* Create the chunk list */
-    oh->nchunks = oh->alloc_nchunks = 1;
-    if(NULL == (oh->chunk = H5FL_SEQ_MALLOC(H5O_chunk_t, (size_t)oh->alloc_nchunks)))
-        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
+    oh->nchunks = 1;
+    oh->alloc_nchunks = 1;
+    oh->chunk = H5FL_SEQ_MALLOC(H5O_chunk_t, (size_t)oh->alloc_nchunks);
+    if (NULL == oh->chunk)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
+                    "memory allocation failed")
 
     /* Initialize the first chunk */
     oh->chunk[0].addr = oh_addr;
@@ -409,30 +554,37 @@ H5O_create(H5F_t *f, size_t size_hint, size_t initial_rc, hid_t ocpl_id,
 
     /* Allocate enough space for the first chunk */
     /* (including space for serializing the object header prefix */
-    if(NULL == (oh->chunk[0].image = H5FL_BLK_CALLOC(chunk_image, oh_size)))
-        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
+    oh->chunk[0].image = H5FL_BLK_CALLOC(chunk_image, oh_size);
+    if(NULL == oh->chunk[0].image)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
+                    "memory allocation failed")
     oh->chunk[0].chunk_proxy = NULL;
 
     /* Put magic # for object header in first chunk */
-    if(oh->version > H5O_VERSION_1)
+    if (H5O_VERSION_1 < oh->version)
         HDmemcpy(oh->chunk[0].image, H5O_HDR_MAGIC, (size_t)H5_SIZEOF_MAGIC);
 
     /* Create the message list */
     oh->nmesgs = 1;
     oh->alloc_nmesgs = H5O_NMESGS;
-    if(NULL == (oh->mesg = H5FL_SEQ_CALLOC(H5O_mesg_t, oh->alloc_nmesgs)))
-        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
+    oh->mesg = H5FL_SEQ_CALLOC(H5O_mesg_t, oh->alloc_nmesgs);
+    if (NULL == oh->mesg)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
+                    "memory allocation failed")
 
-    /* Initialize the initial "null" message, covering the entire first chunk */
+    /* Initialize the initial "null" message; covers the entire first chunk */
     oh->mesg[0].type = H5O_MSG_NULL;
     oh->mesg[0].dirty = TRUE;
     oh->mesg[0].native = NULL;
-    oh->mesg[0].raw = oh->chunk[0].image + (H5O_SIZEOF_HDR(oh) - H5O_SIZEOF_CHKSUM_OH(oh)) + H5O_SIZEOF_MSGHDR_OH(oh);
+    oh->mesg[0].raw = oh->chunk[0].image       \
+                    + H5O_SIZEOF_HDR(oh)       \
+                    - H5O_SIZEOF_CHKSUM_OH(oh) \
+                    + H5O_SIZEOF_MSGHDR_OH(oh);
     oh->mesg[0].raw_size = size_hint - (size_t)H5O_SIZEOF_MSGHDR_OH(oh);
     oh->mesg[0].chunkno = 0;
 
     /* Check for non-zero initial refcount on the object header */
-    if(initial_rc > 0) {
+    if (initial_rc > 0) {
         /* Set the initial refcount & pin the header when its inserted */
         oh->rc = initial_rc;
         insert_flags |= H5AC__PIN_ENTRY_FLAG;
@@ -442,9 +594,11 @@ H5O_create(H5F_t *f, size_t size_hint, size_t initial_rc, hid_t ocpl_id,
     H5_BEGIN_TAG(oh_addr);
 
     /* Cache object header */
-    if(H5AC_insert_entry(f, H5AC_OHDR, oh_addr, oh, insert_flags) < 0)
-        HGOTO_ERROR_TAG(H5E_OHDR, H5E_CANTINSERT, FAIL, "unable to cache object header")
+    if (0 > H5AC_insert_entry(f, H5AC_OHDR, oh_addr, oh, insert_flags))
+        HGOTO_ERROR_TAG(H5E_OHDR, H5E_CANTINSERT, FAIL,
+                        "unable to cache object header")
 
+    /* TODO: is this relevant to the BEGIN/END TAG region? if not, delete */
     /* Reset object header pointer, now that it's been inserted into the cache */
     oh = NULL;
 
@@ -452,20 +606,16 @@ H5O_create(H5F_t *f, size_t size_hint, size_t initial_rc, hid_t ocpl_id,
     H5_END_TAG
 
     /* Set up object location */
-    loc->file = f;
-    loc->addr = oh_addr;
+    loc_out->file = f;
+    loc_out->addr = oh_addr;
 
-    /* Open it */
-    if(H5O_open(loc) < 0)
-        HGOTO_ERROR(H5E_OHDR, H5E_CANTOPENOBJ, FAIL, "unable to open object header")
+    if (0 > H5O_open(loc_out))
+        HGOTO_ERROR(H5E_OHDR, H5E_CANTOPENOBJ, FAIL,
+                    "unable to open object header")
 
 done:
-    if(ret_value < 0 && oh)
-        if(H5O__free(oh) < 0)
-            HDONE_ERROR(H5E_OHDR, H5E_CANTFREE, FAIL, "unable to destroy object header data")
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_create() */
+    FUNC_LEAVE_NOAPI(ret_value);
+} /* H5O__apply_ohdr */
 
 
 /*-------------------------------------------------------------------------
@@ -2686,6 +2836,64 @@ H5O_get_oh_addr(const H5O_t *oh)
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5O_get_oh_flags
+ *
+ * Programmer:	Jacob Smith
+ *		17 August 2018
+ *
+ *-------------------------------------------------------------------------
+ */
+uint8_t
+H5O_get_oh_flags(const H5O_t *oh)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+    HDassert(oh);
+    HDassert(oh->flags);
+    FUNC_LEAVE_NOAPI(oh->flags);
+}
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5O_get_oh_mtime
+ *
+ * Purpose:	Retrieve an object's modification time. Assumes that the
+ *              caller has verified that accessing this variable is appropriate
+ *              to the header in question.
+ *
+ * Programmer:	Jacob Smith
+ *		17 August 2018
+ *
+ *-------------------------------------------------------------------------
+ */
+time_t
+H5O_get_oh_mtime(const H5O_t *oh)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+    HDassert(oh);
+    HDassert(oh->mtime);
+    FUNC_LEAVE_NOAPI(oh->mtime);
+}
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5O_get_oh_version
+ *
+ * Programmer:	Jacob Smith
+ *		17 August 2018
+ *
+ *-------------------------------------------------------------------------
+ */
+uint8_t
+H5O_get_oh_version(const H5O_t *oh)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+    HDassert(oh);
+    HDassert(oh->version);
+    FUNC_LEAVE_NOAPI(oh->version);
+}
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5O_get_rc_and_type
  *
  * Purpose:	Retrieve an object's reference count and type
diff --git a/src/H5Oprivate.h b/src/H5Oprivate.h
index 10063d5..f8154c4 100644
--- a/src/H5Oprivate.h
+++ b/src/H5Oprivate.h
@@ -120,8 +120,14 @@ typedef struct H5O_mesg_t H5O_mesg_t;
 /* If the module using this macro is allowed access to the private variables, access them directly */
 #ifdef H5O_MODULE
 #define H5O_OH_GET_ADDR(O)    ((O)->chunk[0].addr)
+#define H5O_OH_GET_VERSION(O) ((O)->version)
+#define H5O_OH_GET_FLAGS(O)   ((O)->flags)
+#define H5O_OH_GET_MTIME(O)   ((O)->mtime)
 #else /* H5O_MODULE */
 #define H5O_OH_GET_ADDR(O)    (H5O_get_oh_addr(O))
+#define H5O_OH_GET_VERSION(O) (H5O_get_oh_version(O))
+#define H5O_OH_GET_FLAGS(O)   (H5O_get_oh_flags(O))
+#define H5O_OH_GET_MTIME(O)   (H5O_get_oh_mtime(O))
 #endif /* H5O_MODULE */
 
 /* Set the fields in a shared message structure */
@@ -865,6 +871,9 @@ struct H5P_genplist_t;
 H5_DLL herr_t H5O_init(void);
 H5_DLL herr_t H5O_create(H5F_t *f, size_t size_hint, size_t initial_rc,
     hid_t ocpl_id, H5O_loc_t *loc/*out*/);
+H5_DLL H5O_t *H5O__create_ohdr(H5F_t *f, hid_t ocpl_id);
+H5_DLL herr_t H5O__apply_ohdr(H5F_t *f, H5O_t *oh, hid_t ocpl_id,
+    size_t size_hint, size_t initial_rc, H5O_loc_t *loc_out);
 H5_DLL herr_t H5O_open(H5O_loc_t *loc);
 H5_DLL herr_t H5O_close(H5O_loc_t *loc, hbool_t *file_closed/*out*/);
 H5_DLL int H5O_link(const H5O_loc_t *loc, int adjust);
@@ -888,6 +897,9 @@ H5_DLL hid_t H5O_open_name(const H5G_loc_t *loc, const char *name, hbool_t app_r
 H5_DLL herr_t H5O_get_nlinks(const H5O_loc_t *loc, hsize_t *nlinks);
 H5_DLL void *H5O_obj_create(H5F_t *f, H5O_type_t obj_type, void *crt_info, H5G_loc_t *obj_loc);
 H5_DLL haddr_t H5O_get_oh_addr(const H5O_t *oh);
+H5_DLL uint8_t H5O_get_oh_flags(const H5O_t *oh);
+H5_DLL time_t H5O_get_oh_mtime(const H5O_t *oh);
+H5_DLL uint8_t H5O_get_oh_version(const H5O_t *oh);
 H5_DLL herr_t H5O_get_rc_and_type(const H5O_loc_t *oloc, unsigned *rc, H5O_type_t *otype);
 H5_DLL H5AC_proxy_entry_t *H5O_get_proxy(const H5O_t *oh);
 
diff --git a/src/H5Pdcpl.c b/src/H5Pdcpl.c
index cb13ff3..a1799ad 100644
--- a/src/H5Pdcpl.c
+++ b/src/H5Pdcpl.c
@@ -119,6 +119,11 @@
 #define H5D_CRT_EXT_FILE_LIST_COPY H5P__dcrt_ext_file_list_copy
 #define H5D_CRT_EXT_FILE_LIST_CMP  H5P__dcrt_ext_file_list_cmp
 #define H5D_CRT_EXT_FILE_LIST_CLOSE H5P__dcrt_ext_file_list_close
+/* Definitions for dataset object header minimization */
+#define H5D_CRT_MIN_DSET_HDR_SIZE_SIZE sizeof(hbool_t)
+#define H5D_CRT_MIN_DSET_HDR_SIZE_DEF  FALSE
+#define H5D_CRT_MIN_DSET_HDR_SIZE_ENC  H5P__encode_hbool_t
+#define H5D_CRT_MIN_DSET_HDR_SIZE_DEC  H5P__decode_hbool_t
 
 
 /******************/
@@ -211,6 +216,7 @@ static const H5O_layout_t H5D_def_layout_g = H5D_CRT_LAYOUT_DEF;        /* Defau
 static const H5O_fill_t H5D_def_fill_g = H5D_CRT_FILL_VALUE_DEF;        /* Default fill value */
 static const unsigned H5D_def_alloc_time_state_g = H5D_CRT_ALLOC_TIME_STATE_DEF;  /* Default allocation time state */
 static const H5O_efl_t H5D_def_efl_g = H5D_CRT_EXT_FILE_LIST_DEF;                 /* Default external file list */
+static const H5O_ohdr_min_g = H5D_CRT_MIN_DSET_HDR_SIZE_DEF; /* Default object header minimization */
 
 /* Defaults for each type of layout */
 #ifdef H5_HAVE_C99_DESIGNATED_INITIALIZER
@@ -270,6 +276,26 @@ H5P__dcrt_reg_prop(H5P_genclass_t *pclass)
             H5D_CRT_EXT_FILE_LIST_DEL, H5D_CRT_EXT_FILE_LIST_COPY, H5D_CRT_EXT_FILE_LIST_CMP, H5D_CRT_EXT_FILE_LIST_CLOSE) < 0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
 
+    /* Register the object header minimization property */
+    if (0 > H5P_register_real(
+            pclass,                         /* class   */
+            H5D_CRT_MIN_DSET_HDR_SIZE_NAME, /* name    */
+            H5D_CRT_MIN_DSET_HDR_SIZE_SIZE, /* size    */
+            &H5O_ohdr_min_g,                /* default */
+            NULL,                           /* create  */
+            NULL,                           /* set     */
+            NULL,                           /* get     */
+            H5D_CRT_MIN_DSET_HDR_SIZE_ENC,  /* encode  */
+            H5D_CRT_MIN_DSET_HDR_SIZE_DEC,  /* decode  */
+            NULL,                           /* delete  */
+            NULL,                           /* copy    */
+            NULL,                           /* compare */
+            NULL))                          /* close   */
+    {
+       HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL,
+                   "can't insert property into class")
+    }
+
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5P__dcrt_reg_prop() */
@@ -3733,3 +3759,103 @@ done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5Pget_fill_time() */
 
+
+/*-----------------------------------------------------------------------------
+ * Function: H5Pget_dset_no_attrs_hint
+ *
+ * Purpose:
+ *
+ *     Access the flag for whether or not datasets created by the given dcpl
+ *     will be created with a "minimized" object header.
+ *
+ * Return:
+ *
+ *     Failure: Negative value (FAIL)
+ *     Success: Non-negative value (SUCCEED)
+ *
+ * Programmer: Jacob Smith
+ *             14 August 2018
+ *
+ * Modifications: None.
+ *
+ *-----------------------------------------------------------------------------
+ */
+herr_t
+H5Pget_dset_no_attrs_hint(hid_t    dcpl_id,
+                          hbool_t *minimize)
+{
+    hbool_t         setting   = FALSE;
+    H5P_genplist_t *plist     = NULL;
+    herr_t          ret_value = SUCCEED;
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*b", dcpl_id, minimize);
+
+    if (NULL == minimize)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "receiving pointer cannot be NULL")
+
+    plist = H5P_object_verify(dcpl_id, H5P_DATASET_CREATE);
+    if (NULL == plist)
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL,
+                        "can't find object for ID")
+
+    if (0 > H5P_peek(plist, H5D_CRT_MIN_DSET_HDR_SIZE_NAME, &setting))
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL,
+                    "can't get dset oh minimize flag value")
+
+    *minimize = setting;
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* H5Pget_dset_no_attrs_hint */
+
+
+/*-----------------------------------------------------------------------------
+ * Function: H5Pset_dset_no_attrs_hint
+ *
+ * Purpose:
+ *
+ *     Set the dcpl to minimize (or explicitly to not minimized) dataset object
+ *     headers upon creation.
+ *
+ * Return:
+ *
+ *     Failure: Negative value (FAIL)
+ *     Success: Non-negative value (SUCCEED)
+ *
+ * Programmer: Jacob Smith
+ *             14 August 2018
+ *
+ * Modifications: None.
+ *
+ *-----------------------------------------------------------------------------
+ */
+herr_t
+H5Pset_dset_no_attrs_hint(hid_t   dcpl_id,
+                          hbool_t minimize)
+{
+    H5P_genplist_t *plist     = NULL;
+    hbool_t         prev_set  = FALSE;
+    herr_t          ret_value = SUCCEED;
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "ib", dcpl_id, minimize);
+
+    plist = H5P_object_verify(dcpl_id, H5P_DATASET_CREATE);
+    if (NULL == plist)
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL,
+                        "can't find object for ID")
+
+    if (0 > H5P_peek(plist, H5D_CRT_MIN_DSET_HDR_SIZE_NAME, &prev_set))
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL,
+                    "can't get extant dset oh minimize flag value")
+
+    if (0 > H5P_poke(plist, H5D_CRT_MIN_DSET_HDR_SIZE_NAME, &minimize))
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL,
+                    "can't get dset oh minimize flag value")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* H5Pset_dset_no_attrs_hint */
+
diff --git a/src/H5Ppublic.h b/src/H5Ppublic.h
index c5596e5..c2f9b4c 100644
--- a/src/H5Ppublic.h
+++ b/src/H5Ppublic.h
@@ -409,6 +409,8 @@ H5_DLL herr_t H5Pget_alloc_time(hid_t plist_id, H5D_alloc_time_t
 H5_DLL herr_t H5Pset_fill_time(hid_t plist_id, H5D_fill_time_t fill_time);
 H5_DLL herr_t H5Pget_fill_time(hid_t plist_id, H5D_fill_time_t
     *fill_time/*out*/);
+H5_DLL herr_t H5Pget_dset_no_attrs_hint(hid_t dcpl_id, hbool_t *minimize);
+H5_DLL herr_t H5Pset_dset_no_attrs_hint(hid_t dcpl_id, hbool_t minimize);
 
 /* Dataset access property list (DAPL) routines */
 H5_DLL herr_t H5Pset_chunk_cache(hid_t dapl_id, size_t rdcc_nslots,
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 517a620..6c1e0eb 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -234,6 +234,7 @@ set (H5_TESTS
     cache_logging
     cork
     swmr
+    ohdr_min
 )
 
 macro (ADD_H5_EXE file)
diff --git a/test/CMakeTests.cmake b/test/CMakeTests.cmake
index cc6ebb8..44494e9 100644
--- a/test/CMakeTests.cmake
+++ b/test/CMakeTests.cmake
@@ -359,6 +359,8 @@ set (test_CLEANFILES
     lheap.h5
     fheap.h5
     ohdr.h5
+    ohdr_min_a.h5
+    ohdr_min_b.h5
     stab.h5
     extern_*.h5
     extern_*.raw
diff --git a/test/Makefile.am b/test/Makefile.am
index b9aa3fb..551c5ee 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -52,15 +52,15 @@ check_SCRIPTS = $(TEST_SCRIPT)
 # As an exception, long-running tests should occur earlier in the list.
 # This gives them more time to run when tests are executing in parallel.
 TEST_PROG= testhdf5 \
-           cache cache_api cache_image cache_tagging lheap ohdr stab gheap \
-           evict_on_close farray earray btree2 fheap \
+           cache cache_api cache_image cache_tagging lheap ohdr ohdr_min stab \
+           gheap evict_on_close farray earray btree2 fheap \
            pool accum hyperslab istore bittests dt_arith page_buffer \
            dtypes dsets cmpd_dset filter_fail extend direct_chunk external efc \
-		   objcopy links unlink twriteorder big mtime fillval mount \
-		   flush1 flush2 app_ref enum set_extent ttsafe enc_dec_plist \
-		   enc_dec_plist_cross_platform getname vfd ntypes dangle dtransform \
-		   reserved cross_read freespace mf vds file_image unregister \
-		   cache_logging cork swmr
+           objcopy links unlink twriteorder big mtime fillval mount \
+           flush1 flush2 app_ref enum set_extent ttsafe enc_dec_plist \
+           enc_dec_plist_cross_platform getname vfd ntypes dangle dtransform \
+           reserved cross_read freespace mf vds file_image unregister \
+           cache_logging cork swmr
 
 # List programs to be built when testing here.
 # error_test and err_compat are built at the same time as the other tests, but executed by testerror.sh.
@@ -165,6 +165,7 @@ CHECK_CLEANFILES+=accum.h5 cmpd_dset.h5 compact_dataset.h5 dataset.h5 dset_offse
     extend.h5 istore.h5 extlinks*.h5 frspace.h5 links*.h5 \
     sys_file1 tfile[1-7].h5 th5s[1-4].h5 lheap.h5 fheap.h5 ohdr.h5 \
     stab.h5 extern_[1-5].h5 extern_[1-4][rw].raw gheap[0-4].h5 \
+    ohdr_min_a.h5 ohdr_min_b.h5 \
     dt_arith[1-2] links.h5 links[0-6]*.h5 extlinks[0-15].h5 tmp \
     big.data big[0-9][0-9][0-9][0-9][0-9].h5  \
     stdio.h5 sec2.h5 dtypes[0-9].h5 dtypes1[0].h5 dt_arith[1-2].h5 tattr.h5 \
diff --git a/test/dsets.c b/test/dsets.c
index d23f438..94c967e 100644
--- a/test/dsets.c
+++ b/test/dsets.c
@@ -13034,6 +13034,113 @@ test_versionbounds()
     return -1;
 } /* test_versionbounds() */
 
+
+/*-----------------------------------------------------------------------------
+ * Function:   test_object_header_minimization_dcpl
+ *
+ * Purpose:    Test the "datset object header minimization" property as part of
+ *             the DCPL.
+ *
+ * Return:     Success/pass:   0
+ *             Failure/error: -1
+ *
+ * Programmer: Jacob Smith
+ *             15 Aug 2018
+ *
+ * Changes:    None.
+ *-----------------------------------------------------------------------------
+ */
+static herr_t
+test_object_header_minimization_dcpl(void)
+{
+    hid_t    dcpl_id  = -1;
+    hid_t    file_id  = -1;
+    hbool_t  minimize = FALSE;
+
+    TESTING("dcpl flags to minimize dataset object header");
+
+    /*********/
+    /* SETUP */
+    /*********/
+
+    file_id = H5Fcreate(
+            "some_arbitrary_filename",
+            H5F_ACC_TRUNC,
+            H5P_DEFAULT,
+            H5P_DEFAULT);
+    if (0 > file_id)
+        FAIL_PUTS_ERROR("unable to create test file\n");
+
+    dcpl_id = H5Pcreate(H5P_DATASET_CREATE);
+    if (0 > dcpl_id)
+        FAIL_PUTS_ERROR("unable to create DCPL\n");
+
+    /*********/
+    /* TESTS */
+    /*********/
+
+    /* TEST default value (not set explicitly)
+     */
+    if (FAIL == H5Pget_dset_no_attrs_hint(dcpl_id, &minimize))
+        FAIL_PUTS_ERROR("unable to get minimize value\n");
+    if (FALSE != minimize)
+        FAIL_PUTS_ERROR("Expected FALSE default but was not!\n");
+
+    /* TEST FALSE-set value
+     */
+    if (FAIL == H5Pset_dset_no_attrs_hint(dcpl_id, FALSE))
+        FAIL_PUTS_ERROR("unable to set minimize value to FALSE\n");
+    if (FAIL == H5Pget_dset_no_attrs_hint(dcpl_id, &minimize))
+        FAIL_PUTS_ERROR("unable to get minimize value\n");
+    if (FALSE != minimize)
+        FAIL_PUTS_ERROR("Expected FALSE default but was not!\n");
+
+    /* TEST TRUE-set value
+     */
+    if (FAIL == H5Pset_dset_no_attrs_hint(dcpl_id, TRUE))
+        FAIL_PUTS_ERROR("unable to set minimize value to TRUE\n");
+    if (FAIL == H5Pget_dset_no_attrs_hint(dcpl_id, &minimize))
+        FAIL_PUTS_ERROR("unable to get minimize value\n");
+    if (TRUE != minimize)
+        FAIL_PUTS_ERROR("Expected TRUE default but was not!\n");
+
+    /* TEST error cases
+     */
+    H5E_BEGIN_TRY {
+        if (SUCCEED == H5Pget_dset_no_attrs_hint(-1, &minimize))
+            FAIL_PUTS_ERROR("Invalid DCPL ID should fail\n");
+
+        if (SUCCEED == H5Pset_dset_no_attrs_hint(-1, FALSE))
+            FAIL_PUTS_ERROR("Invalid DCPL ID should fail\n");
+
+        if (SUCCEED == H5Pset_dset_no_attrs_hint(-1, TRUE))
+            FAIL_PUTS_ERROR("Invalid DCPL ID should fail\n");
+
+        if (SUCCEED == H5Pget_dset_no_attrs_hint(dcpl_id, NULL))
+            FAIL_PUTS_ERROR("NULL out pointer should fail\n");
+    } H5E_END_TRY;
+
+    /************/
+    /* TEARDOWN */
+    /************/
+
+    if (FAIL == H5Fclose(file_id))
+        FAIL_PUTS_ERROR("can't close FILE");
+
+    if (FAIL == H5Pclose(dcpl_id))
+        FAIL_PUTS_ERROR("unable to close DCPL\n");
+
+    PASSED();
+    return 0;
+
+error:
+    H5E_BEGIN_TRY {
+        H5Pclose(dcpl_id);
+        H5Fclose(file_id);
+    } H5E_END_TRY;
+    return -1;
+} /* test_object_header_minimization_dcpl */
+
 
 /*-------------------------------------------------------------------------
  * Function:    main
@@ -13234,6 +13341,8 @@ main(void)
     /* Tests version bounds using its own file */
     nerrors += (test_versionbounds() < 0             ? 1 : 0);
 
+    nerrors += (test_object_header_minimization_dcpl() < 0 ? 1 : 0);
+
     /* Run misc tests */
     nerrors += dls_01_main();
 
diff --git a/test/enc_dec_plist.c b/test/enc_dec_plist.c
index 36db2d0..cee38f3 100644
--- a/test/enc_dec_plist.c
+++ b/test/enc_dec_plist.c
@@ -146,6 +146,9 @@ main(void)
     if((H5Pset_fill_value(dcpl, H5T_NATIVE_DOUBLE, &fill)) < 0)
         FAIL_STACK_ERROR
 
+    if((H5Pset_dset_no_attrs_hint(dcpl, FALSE)) < 0)
+        FAIL_STACK_ERROR
+
     max_size[0] = 100;
     if((H5Pset_external(dcpl, "ext1.data", (off_t)0, 
                          (hsize_t)(max_size[0] * sizeof(int)/4))) < 0)
diff --git a/test/gen_plist.c b/test/gen_plist.c
index 62693bd..d8096e3 100644
--- a/test/gen_plist.c
+++ b/test/gen_plist.c
@@ -125,6 +125,9 @@ main(void)
     if((ret = H5Pset_fill_value(dcpl1, H5T_STD_I32BE, &fill)) < 0)
         assert(ret > 0);
 
+    if((ret = H5Pset_dset_no_attrs_hint(dcpl1, FALSE)) < 0)
+        assert(ret > 0);
+
     max_size[0] = 100;
     if((ret = H5Pset_external(dcpl1, "ext1.data", (off_t)0, 
                          (hsize_t)(max_size[0] * sizeof(int)/4))) < 0)
diff --git a/test/tfile.c b/test/tfile.c
index d3134f8..96e469c 100644
--- a/test/tfile.c
+++ b/test/tfile.c
@@ -7051,6 +7051,144 @@ test_incr_filesize(void)
 
 /****************************************************************
 **
+**  test_min_dset_ohdr():
+**    Test API calls to toggle dataset object header minimization.
+**
+**  TODO (as separate function?):
+**    + setting persists between close and (re)open?
+**    + dataset header sizes created while changing value of toggle
+**
+****************************************************************/
+static void
+test_min_dset_ohdr(void)
+{
+    const char my_filename[] = "some_arbitrary_filename";
+    hid_t      file_id       = -1;
+    hid_t      file2_id      = -1;
+    hbool_t    minimize;
+
+    MESSAGE(5, ("Testing dataset object header minimization\n"));
+
+    /*********/
+    /* SETUP */
+    /*********/
+
+    file_id = H5Fcreate(
+            my_filename,
+            H5F_ACC_TRUNC,
+            H5P_DEFAULT,
+            H5P_DEFAULT);
+    CHECK_I(file_id, "H5Fcreate");
+
+    /*********/
+    /* TESTS */
+    /*********/
+
+    /*----------------------------------------
+     * TEST default value
+     */
+    VERIFY(H5Fget_dset_no_attrs_hint(file_id, &minimize),
+           SUCCEED,
+           "H5Fget_dset_no_attrs_hint");
+    VERIFY(minimize,
+           FALSE,
+           "getting default dset minimize flag value");
+
+    /*----------------------------------------
+     * TEST set to TRUE
+     */
+    VERIFY(H5Fset_dset_no_attrs_hint(file_id, TRUE),
+           SUCCEED,
+           "H5Fset_dset_no_attrs_hint");
+    VERIFY(H5Fget_dset_no_attrs_hint(file_id, &minimize),
+           SUCCEED,
+           "H5Fget_dset_no_attrs_hint");
+    VERIFY(minimize,
+           TRUE,
+           "getting set-TRUE dset minimize flag value");
+
+    /*----------------------------------------
+     * TEST second file open on same filename
+     */
+    file2_id = H5Fopen(
+            my_filename,
+            H5F_ACC_RDWR,
+            H5P_DEFAULT);
+    CHECK_I(file2_id, "H5Fopen");
+
+    /* verify TRUE setting on second open */
+    VERIFY(H5Fget_dset_no_attrs_hint(file_id, &minimize),
+           SUCCEED,
+           "H5Fget_dset_no_attrs_hint");
+    VERIFY(minimize,
+           TRUE,
+           "getting set-TRUE dset minimize flag value");
+
+    /* re-set to FALSE on first open */
+    VERIFY(H5Fset_dset_no_attrs_hint(file_id, FALSE),
+           SUCCEED,
+           "H5Fset_dset_no_attrs_hint");
+
+    /* verify FALSE set on both opens */
+    VERIFY(H5Fget_dset_no_attrs_hint(file_id, &minimize),
+           SUCCEED,
+           "H5Fget_dset_no_attrs_hint");
+    VERIFY(minimize,
+           FALSE,
+           "getting set-FALSE dset minimize flag value");
+    VERIFY(H5Fget_dset_no_attrs_hint(file2_id, &minimize),
+           SUCCEED,
+           "H5Fget_dset_no_attrs_hint");
+    VERIFY(minimize,
+           FALSE,
+           "getting set-FALSE dset minimize flag value");
+
+    /* re-set to TRUE on second open */
+    VERIFY(H5Fset_dset_no_attrs_hint(file2_id, TRUE),
+           SUCCEED,
+           "H5Fset_dset_no_attrs_hint");
+
+    /* verify TRUE set on both opens */
+    VERIFY(H5Fget_dset_no_attrs_hint(file_id, &minimize),
+           SUCCEED,
+           "H5Fget_dset_no_attrs_hint");
+    VERIFY(minimize,
+           TRUE,
+           "getting set-FALSE dset minimize flag value");
+    VERIFY(H5Fget_dset_no_attrs_hint(file2_id, &minimize),
+           SUCCEED,
+           "H5Fget_dset_no_attrs_hint");
+    VERIFY(minimize,
+           TRUE,
+           "getting set-FALSE dset minimize flag value");
+
+    /*----------------------------------------
+     * TEST error cases
+     */
+    H5E_BEGIN_TRY {
+        VERIFY(H5Fset_dset_no_attrs_hint(-1, TRUE),
+               FAIL,
+               "trying to set with invalid file ID");
+
+        VERIFY(H5Fget_dset_no_attrs_hint(-1, &minimize),
+               FAIL,
+               "trying to get with invalid file ID");
+
+        VERIFY(H5Fget_dset_no_attrs_hint(file_id, NULL),
+               FAIL,
+               "trying to get with invalid pointer");
+    } H5E_END_TRY;
+
+    /************/
+    /* TEARDOWN */
+    /************/
+
+    VERIFY(H5Fclose(file_id), SUCCEED, "H5Fclose");
+    VERIFY(H5Fclose(file2_id), SUCCEED, "H5Fclose");
+} /* end test_min_dset_ohdr() */
+
+/****************************************************************
+**
 **  test_deprec():
 **    Test deprecated functionality.
 **
@@ -7336,6 +7474,7 @@ test_file(void)
     test_libver_macros();                       /* Test the macros for library version comparison */
     test_libver_macros2();                      /* Test the macros for library version comparison */
     test_incr_filesize();                       /* Test H5Fincrement_filesize() and H5Fget_eoa() */
+    test_min_dset_ohdr();                       /* Test datset object header minimization */
 #ifndef H5_NO_DEPRECATED_SYMBOLS
     test_deprec();                              /* Test deprecated routines */
 #endif /* H5_NO_DEPRECATED_SYMBOLS */