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<!-- #EndLibraryItem --><h1>HDF5 Library Environment Variables and Configuration Parameters</h1>

<h2>1. Environment Variables</h2>

The HDF5 library uses UNIX environment variables to control
or adjust certain library features at runtime.  The variables and 
their defined effects are as follows:

<dir>
<dl>
    <dt><tt>HDF5_DEBUG</tt>
        <dd>Defines a list of debugging switches documented in the
            <a href="Debugging.html">Debugging</a> section of the
            <cite>HDF5 User's Guide</cite>.

    <dt><tt>HDF5_NOCLEANUP</tt>
        <dd>When set to a non-empty value, the programs in the test
            directory do not remove temporary HDF5 data files.
            The default is for each test to remove the files before exit.

    <dt><tt>HDF5_MPI_OPT_TYPES</tt> 
            &nbsp;&nbsp;(for parallel beta version only)
        <dd>When set to <code>1</code>, PHDF5 will use the MPI optimized 
            code to perform parallel read/write accesses to datasets.
            Currently, this optimization fails when accessing extendable
            datasets.  The default is not to use the optimized code.

    <dt><tt>HDF5_MPI_1_METAWRITE</tt> 
            &nbsp;&nbsp;(for parallel beta version only)
        <dd>When set to <code>1</code>, PHDF5 will write the metadata 
            via process 0 of each opened parallel HDF5 file.  This should 
            improve I/O throughput.  The default is not to use this 
            optimization.

</dl>
</dir>

<h2>2. Configuration Parameters</h2>

The HDF5 configuration script accepts a list of parameters to control
configuration features when creating the Makefiles for the library.  
The command
<br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;configure --help </code>
<br>
will display the current list of parameters and their effects. 
<br><br>


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Describes HDF5 Release 1.4.5, February 2003
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Last modified: 13 December 1999
 
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