<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>DbEnv::mutex_set_max()</title> <link rel="stylesheet" href="apiReference.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> <link rel="start" href="index.html" title="Berkeley DB C++ API Reference" /> <link rel="up" href="mutex.html" title="Chapter 10. Mutex Methods" /> <link rel="prev" href="mutexset_increment.html" title="DbEnv::mutex_set_increment()" /> <link rel="next" href="mutexset_tas_spins.html" title="DbEnv::mutex_set_tas_spins()" /> </head> <body> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">DbEnv::mutex_set_max()</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="mutexset_increment.html">Prev</a> </td> <th width="60%" align="center">Chapter 10. Mutex Methods </th> <td width="20%" align="right"> <a accesskey="n" href="mutexset_tas_spins.html">Next</a></td> </tr> </table> <hr /> </div> <div class="sect1" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h2 class="title" style="clear: both"><a id="mutexset_max"></a>DbEnv::mutex_set_max()</h2> </div> </div> </div> <pre class="programlisting">#include <db_cxx.h> int DbEnv::mutex_set_max(u_int32_t max); </pre> <p> Configure the total number of mutexes to allocate. </p> <p> Berkeley DB allocates a default number of mutexes based on the initial configuration of the database environment. That default calculation may be too small if the application has an unusual need for mutexes (for example, if the application opens an unexpectedly large number of databases) or too large (if the application is trying to minimize its memory footprint). The <code class="methodname">DbEnv::mutex_set_max()</code> method is used to specify an absolute number of mutexes to allocate. </p> <p> Calling the <code class="methodname">DbEnv::mutex_set_max()</code> method discards any value previously set using the <code class="methodname">DbEnv::mutex_set_increment()</code> method. </p> <p> The database environment's total number of mutexes may also be configured using the environment's <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file. The syntax of the entry in that file is a single line with the string "mutex_set_max", one or more whitespace characters, and the total number of mutexes. Because the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file is read when the database environment is opened, it will silently overrule configuration done before that time. </p> <p> The <code class="methodname">DbEnv::mutex_set_max()</code> method configures a database environment, not only operations performed using the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle. </p> <p> The <code class="methodname">DbEnv::mutex_set_max()</code> method may not be called after the <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method is called. If the database environment already exists when <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> is called, the information specified to <code class="methodname">DbEnv::mutex_set_max()</code> will be ignored. </p> <p> The <code class="methodname">DbEnv::mutex_set_max()</code> <span> <span> method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success. </span> </span> </p> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1699485"></a>Parameters</h3> </div> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1699512"></a>max</h4> </div> </div> </div> <p> The <span class="bold"><strong>max</strong></span> parameter is the absolute number of mutexes to allocate. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1699661"></a>Errors</h3> </div> </div> </div> <p> The <code class="methodname">DbEnv::mutex_set_max()</code> <span> <span> method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a> exception, encapsulating one of the following non-zero errors, or return one of the following non-zero errors: </span> </span> </p> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1699496"></a>EINVAL</h4> </div> </div> </div> <p> An invalid flag value or parameter was specified. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1699497"></a>Class</h3> </div> </div> </div> <p> <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1699566"></a>See Also</h3> </div> </div> </div> <p> <a class="xref" href="mutex.html#mutexlist" title="Mutex Methods">Mutex Methods</a> </p> </div> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="mutexset_increment.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="mutex.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="mutexset_tas_spins.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">DbEnv::mutex_set_increment() </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> DbEnv::mutex_set_tas_spins()</td> </tr> </table> </div> </body> </html>