1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"> 4 <head> 5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 6 <title>DbEnv::set_mp_max_openfd()</title> 7 <link rel="stylesheet" href="apiReference.css" type="text/css" /> 8 <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> 9 <link rel="start" href="index.html" title="Berkeley DB C++ API Reference" /> 10 <link rel="up" href="memp.html" title="Chapter 9. The DbMpoolFile Handle" /> 11 <link rel="prev" href="envset_cachesize.html" title="DbEnv::set_cachesize()" /> 12 <link rel="next" href="mempset_mp_max_write.html" title="DbEnv::set_mp_max_write()" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">DbEnv::set_mp_max_openfd()</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="envset_cachesize.html">Prev</a> </td> 22 <th width="60%" align="center">Chapter 9. 23 The DbMpoolFile Handle 24 </th> 25 <td width="20%" align="right"> <a accesskey="n" href="mempset_mp_max_write.html">Next</a></td> 26 </tr> 27 </table> 28 <hr /> 29 </div> 30 <div class="sect1" lang="en" xml:lang="en"> 31 <div class="titlepage"> 32 <div> 33 <div> 34 <h2 class="title" style="clear: both"><a id="mempset_mp_max_openfd"></a>DbEnv::set_mp_max_openfd()</h2> 35 </div> 36 </div> 37 </div> 38 <pre class="programlisting">#include <db_cxx.h> 39 40int 41DbEnv::set_mp_max_openfd(int maxopenfd); </pre> 42 <p> 43 The <code class="methodname">DbEnv::set_mp_max_openfd()</code> method limits the number of file 44 descriptors the library will open concurrently when flushing dirty 45 pages from the cache. 46 </p> 47 <p> 48 The database environment's limit on open file descriptors to flush 49 dirty pages may also be configured using the environment's 50 <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file. The 51 syntax of the entry in that file is a single line with the string 52 "set_max_openfd", one or more whitespace characters, and the number of 53 open file descriptors. Because the 54 <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file is 55 read when the database environment is opened, it will silently 56 overrule configuration done before that time. 57 </p> 58 <p> 59 The <a class="xref" href="mempset_mp_max_openfd.html" title="DbEnv::set_mp_max_openfd()">DbEnv::set_mp_max_openfd()</a> 60 method configures a database environment, not only operations 61 performed using the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle. 62 </p> 63 <p> 64 The <code class="methodname">DbEnv::set_mp_max_openfd()</code> <span> 65 66 <span> 67 method either returns a non-zero error value or throws an 68 exception that encapsulates a non-zero error value on 69 failure, and returns 0 on success. 70 </span> 71 </span> 72 </p> 73 <div class="sect2" lang="en" xml:lang="en"> 74 <div class="titlepage"> 75 <div> 76 <div> 77 <h3 class="title"><a id="id1692951"></a>Parameters</h3> 78 </div> 79 </div> 80 </div> 81 <div class="sect3" lang="en" xml:lang="en"> 82 <div class="titlepage"> 83 <div> 84 <div> 85 <h4 class="title"><a id="id1692801"></a>maxopenfd</h4> 86 </div> 87 </div> 88 </div> 89 <p> 90 The maximum number of file descriptors that may be concurrently opened 91 by the library when flushing dirty pages from the cache. 92 </p> 93 </div> 94 </div> 95 <div class="sect2" lang="en" xml:lang="en"> 96 <div class="titlepage"> 97 <div> 98 <div> 99 <h3 class="title"><a id="id1692882"></a>Errors</h3> 100 </div> 101 </div> 102 </div> 103 <p> 104 The <code class="methodname">DbEnv::set_mp_max_openfd()</code> <span> 105 106 <span> 107 method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a> 108 exception, encapsulating one of the following non-zero errors, or return one 109 of the following non-zero errors: 110 </span> 111 </span> 112 </p> 113 <div class="sect3" lang="en" xml:lang="en"> 114 <div class="titlepage"> 115 <div> 116 <div> 117 <h4 class="title"><a id="id1692939"></a>EINVAL</h4> 118 </div> 119 </div> 120 </div> 121 <p> 122 An invalid flag value or parameter was specified. 123 </p> 124 </div> 125 </div> 126 <div class="sect2" lang="en" xml:lang="en"> 127 <div class="titlepage"> 128 <div> 129 <div> 130 <h3 class="title"><a id="id1692936"></a>Class</h3> 131 </div> 132 </div> 133 </div> 134 <p> 135 <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> 136 </p> 137 </div> 138 <div class="sect2" lang="en" xml:lang="en"> 139 <div class="titlepage"> 140 <div> 141 <div> 142 <h3 class="title"><a id="id1693270"></a>See Also</h3> 143 </div> 144 </div> 145 </div> 146 <p> 147 <a class="xref" href="memp.html#memplist" title="Memory Pools and Related Methods">Memory Pools and Related Methods</a> 148 </p> 149 </div> 150 </div> 151 <div class="navfooter"> 152 <hr /> 153 <table width="100%" summary="Navigation footer"> 154 <tr> 155 <td width="40%" align="left"><a accesskey="p" href="envset_cachesize.html">Prev</a> </td> 156 <td width="20%" align="center"> 157 <a accesskey="u" href="memp.html">Up</a> 158 </td> 159 <td width="40%" align="right"> <a accesskey="n" href="mempset_mp_max_write.html">Next</a></td> 160 </tr> 161 <tr> 162 <td width="40%" align="left" valign="top">DbEnv::set_cachesize() </td> 163 <td width="20%" align="center"> 164 <a accesskey="h" href="index.html">Home</a> 165 </td> 166 <td width="40%" align="right" valign="top"> DbEnv::set_mp_max_write()</td> 167 </tr> 168 </table> 169 </div> 170 </body> 171</html> 172