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146 lines
6.2 KiB
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<title>DbMpoolFile::set_clear_len()</title>
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB C++ API Reference" />
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<link rel="up" href="memp.html" title="Chapter 9. The DbMpoolFile Handle" />
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<p>Library Version 11.2.5.2</p>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">DbMpoolFile::set_clear_len()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="mempget_priority.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 9.
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The DbMpoolFile Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="mempset_fileid.html">Next</a></td>
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</tr>
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<hr />
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="mempset_clear_len"></a>DbMpoolFile::set_clear_len()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db_cxx.h>
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int DbMpoolFile::set_clear_len(u_int32_t len); </pre>
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<p>
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The <code class="methodname">DbMpoolFile::set_clear_len()</code> method sets the number of initial
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bytes in a page that should be set to nul when the page is created as
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a result of the
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<a class="link" href="mempfget.html#mpoolfget_DB_MPOOL_CREATE">DB_MPOOL_CREATE</a>
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or <a class="link" href="mempfget.html#mpoolfget_DB_MPOOL_NEW">DB_MPOOL_NEW</a>
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flags specified to <a class="xref" href="mempfget.html" title="DbMpoolFile::get()">DbMpoolFile::get()</a>. If no
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clear length is specified, the entire page is cleared when it is
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created.
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</p>
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<p>
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The <code class="methodname">DbMpoolFile::set_clear_len()</code> method configures a file in the
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cache, not only operations performed using the specified
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<a class="link" href="memp.html" title="Chapter 9. The DbMpoolFile Handle">DbMpoolFile</a> handle.
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</p>
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<p>
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The <code class="methodname">DbMpoolFile::set_clear_len()</code> method may not be called after the
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<a class="xref" href="mempfopen.html" title="DbMpoolFile::open()">DbMpoolFile::open()</a>
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method is called. If the file is already open in the cache when
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<a class="xref" href="mempfopen.html" title="DbMpoolFile::open()">DbMpoolFile::open()</a> is
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called, the information specified to <code class="methodname">DbMpoolFile::set_clear_len()</code>
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must be consistent with the existing file or an error will be returned.
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</p>
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<p>
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The <code class="methodname">DbMpoolFile::set_clear_len()</code> <span>
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<span>
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method either returns a non-zero error value or throws an
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exception that encapsulates a non-zero error value on
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failure, and returns 0 on success.
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</span>
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</span>
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</p>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3650285"></a>Parameters</h3>
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</div>
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</div>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3650274"></a>len</h4>
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>len</strong></span> parameter is the number of
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initial bytes in a page that should be set to nul when the page is
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created. A value of 0 results in the entire page being set to nul
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bytes.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3650175"></a>Class</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>, <a class="link" href="memp.html" title="Chapter 9. The DbMpoolFile Handle">DbMpoolFile</a>
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</p>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3650244"></a>See Also</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="xref" href="memp.html#memplist" title="Memory Pools and Related Methods">Memory Pools and Related Methods</a>
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</p>
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</div>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="mempget_priority.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="memp.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="mempset_fileid.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">DbMpoolFile::get_priority() </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> DbMpoolFile::set_fileid()</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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