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307 lines
11 KiB
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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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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DbEnv::mutex_stat()</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="mutexset_tas_spins.html" title="DbEnv::mutex_set_tas_spins()" />
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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_stat()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="mutexset_tas_spins.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="mutexstat_print.html">Next</a></td>
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</table>
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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="mutexstat"></a>DbEnv::mutex_stat()</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_stat(DB_MUTEX_STAT **statp, u_int32_t flags); </pre>
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<p>
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The <code class="methodname">DbEnv::mutex_stat()</code> method returns the mutex subsystem
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statistics.
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</p>
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<p>
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The <code class="methodname">DbEnv::mutex_stat()</code> method creates a statistical structure of
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type <code class="literal">DB_MUTEX_STAT</code> and copies a pointer to it into a user-specified
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memory location.
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</p>
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<p>
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Statistical structures are stored in allocated memory. If
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application-specific allocation routines have been declared (see
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<a class="xref" href="envset_alloc.html" title="DbEnv::set_alloc()">DbEnv::set_alloc()</a>
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for more information), they are used to allocate the memory;
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otherwise, the standard C library <span class="bold"><strong>malloc</strong></span>(3) is used. The caller is responsible
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for deallocating the memory. To deallocate the memory, free the
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memory reference; references inside the returned memory need not be
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individually freed.
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</p>
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<p>
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The following <code class="literal">DB_MUTEX_STAT</code> fields will be filled in:
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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>
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<span class="bold"><strong>u_int32_t st_mutex_align;</strong></span>
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</p>
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<p>
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The mutex alignment, in bytes.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>int st_mutex_cnt;</strong></span>
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</p>
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<p>
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The total number of mutexes configured.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_mutex_free;</strong></span>
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</p>
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<p>
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The number of mutexes currently available.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_mutex_init;</strong></span>
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</p>
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<p>
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The initial number of mutexes configured.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_mutex_inuse;</strong></span>
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</p>
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<p>
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The number of mutexes currently in use.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_mutex_inuse_max;</strong></span>
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</p>
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<p>
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The maximum number of mutexes ever in use.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_mutex_max;</strong></span>
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</p>
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<p>
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The maximum number of mutexes.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_mutex_tas_spins;</strong></span>
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</p>
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<p>
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The number of times test-and-set mutexes will spin without blocking.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_region_wait;</strong></span>
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</p>
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<p>
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The number of times that a thread of control was forced to wait before
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obtaining the mutex region mutex.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_region_nowait;</strong></span>
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</p>
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<p>
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The number of times that a thread of control was able to obtain the
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mutex region mutex without waiting.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>roff_t st_regmax;</strong></span>
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</p>
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<p>
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The max size of the mutex region size.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>roff_t st_regsize;</strong></span>
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</p>
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<p>
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The size of the mutex region, in bytes.
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</p>
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</li>
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</ul>
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</div>
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<p>
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The <code class="methodname">DbEnv::mutex_stat()</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_stat()</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="id3654424"></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="id3654258"></a>statp</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>statp</strong></span> parameter references memory
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into which a pointer to the allocated statistics structure is copied.
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</p>
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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="id3654485"></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 the following value:
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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>
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<code class="literal">DB_STAT_CLEAR</code>
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</p>
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<p>
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Reset statistics after returning their values.
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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>
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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="id3654304"></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_stat()</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="id3654702"></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="id3654680"></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="id3654628"></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="mutexset_tas_spins.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="mutexstat_print.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">DbEnv::mutex_set_tas_spins() </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_stat_print()</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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