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HTML
206 lines
7.8 KiB
HTML
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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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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DbEnv::mutex_alloc()</title>
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<link rel="stylesheet" href="apiReference.css" type="text/css" />
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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="mutex.html" title="Chapter 10. Mutex Methods" />
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<link rel="prev" href="mutex.html" title="Chapter 10. Mutex Methods" />
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<link rel="next" href="mutexfree.html" title="DbEnv::mutex_free()" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 11.2.5.2</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">DbEnv::mutex_alloc()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="mutex.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 10.
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Mutex Methods
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="mutexfree.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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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="mutexalloc"></a>DbEnv::mutex_alloc()</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
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DbEnv::mutex_alloc(u_int32_t flags, db_mutex_t *mutexp);</pre>
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<p>
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The <code class="methodname">DbEnv::mutex_alloc()</code> method allocates a mutex and returns a
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reference to it into the memory specified by <span class="bold"><strong>mutexp</strong></span>.
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</p>
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<p>
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The <code class="methodname">DbEnv::mutex_alloc()</code> method may not be called before the
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<a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method is called.
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</p>
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<p>
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The <code class="methodname">DbEnv::mutex_alloc()</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="id3651743"></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="id3651750"></a>flags</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>flags</strong></span> parameter must be set to 0
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or by bitwise inclusively <span class="bold"><strong>OR</strong></span>'ing
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together one or more of the following values:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p><a id="alloc_DB_MUTEX_PROCESS_ONLY"></a>
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<code class="literal">DB_MUTEX_PROCESS_ONLY</code>
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</p>
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<p>
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The mutex is associated with a single process. The
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<a class="xref" href="envfailchk.html" title="DbEnv::failchk()">DbEnv::failchk()</a> method will
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release mutexes held by any process which has exited.
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</p>
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</li>
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<li>
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<p><a id="alloc_DB_MUTEX_SELF_BLOCK"></a>
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<code class="literal">DB_MUTEX_SELF_BLOCK</code>
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</p>
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<p>
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The mutex must be self-blocking. That is, if a thread of control
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locks the mutex and then attempts to lock the mutex again, the thread
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of control will block until another thread of control releases the
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original lock on the mutex, allowing the original thread of control to
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lock the mutex the second time. Attempting to re-acquire a mutex for
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which the <code class="literal">DB_MUTEX_SELF_BLOCK</code> flag was not specified will result in
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undefined behavior.
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</p>
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</li>
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</ul>
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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="id3652073"></a>mutexp</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>mutexp</strong></span> parameter references
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memory into which the mutex reference is copied.
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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="id3651304"></a>Errors</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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The <code class="methodname">DbEnv::mutex_alloc()</code> <span>
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<span>
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method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
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exception, encapsulating one of the following non-zero errors, or return one
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of the following non-zero errors:
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</span>
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</span>
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</p>
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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="id3652217"></a>EINVAL</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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An invalid flag value or parameter was specified.
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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="id3652184"></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>
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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="id3652130"></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="mutex.html#mutexlist" title="Mutex Methods">Mutex 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="mutex.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="mutex.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="mutexfree.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">Chapter 10.
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Mutex Methods
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</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"> DbEnv::mutex_free()</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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