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<h1 class="topictitle1">Large file support</h1>
<div><p><span>The integrated file system APIs are enhanced
to allow your applications to store and manipulate very large files. The integrated
file system allows stream file sizes up to approximately 1 TB (1 TB equals
approximately 1 099 511 627 776 bytes) in the <span class="q">"root"</span> (/), QOpenSys, and
user-defined file systems.</span></p>
<div class="section"><p>The integrated file system provides a set of 64-bit UNIX-type
APIs and allows an easy mapping of existing 32-bit APIs to 64-bit APIs that
are capable of accessing large file sizes and offsets by using eight byte
integer arguments.</p>
</div>
<div class="section"><p>The following situations are provided to allow applications
to use large file support:</p>
</div>
<div class="section"> <ul><li>If the macro label <samp class="codeph">_LARGE_FILE_API</samp> is defined at compile
time, applications have access to APIs and data structures that are 64-bit
enabled. For example, an application intending to use <span class="apiname">stat64()</span> API
and <samp class="codeph">stat64</samp> structure will need to define <samp class="codeph">_LARGE_FILE_API</samp> at
compile time.</li>
<li>If the macro label <samp class="codeph">_LARGE_FILES</samp> is defined by the applications
at compile time, existing APIs and data structures are mapped to their 64-bit
versions. For example, if an application defines <samp class="codeph">_LARGE_FILES</samp> at
compile time, a call to <span class="apiname">stat()</span> API is mapped to <span class="apiname">stat64()</span> API
and <span class="apiname">stat()</span>structure is mapped to <span class="apiname">stat64()</span> structure.</li>
</ul>
</div>
<div class="section"><p>The applications that intend to use the large file support can
either define <samp class="codeph">_LARGE_FILE_API</samp> at compile time and code directly
to the 64-bit APIs, or they can define <samp class="codeph">_LARGE_FILES</samp> at compile
time. All the appropriate APIs and data structures are then mapped to the
64-bit version automatically.</p>
</div>
<div class="section"><p>Applications that do not intend to use the large file support
are not impacted and can continue to use integrated file system APIs without
any changes.</p>
</div>
</div>
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<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaaxprogapi.htm" title="Many of the application program interfaces (APIs) that perform operations on integrated file system objects are in the form of C language functions.">Perform operations using APIs</a></div>
</div>
<div class="relinfo"><strong>Related information</strong><br />
<div><a href="../apis/unix2.htm">Integrated file system APIs</a></div>
<div><a href="../apis/stat64.htm">stat64()</a></div>
<div><a href="../apis/stat.htm">stat()</a></div>
</div>
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