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>Chapter 9. The DbMpoolFile Handle</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="index.html" title="Berkeley DB C++ API Reference" /> 11 <link rel="prev" href="logcompare.html" title="DbEnv::log_compare()" /> 12 <link rel="next" href="dbget_mpf.html" title="Db::get_mpf()" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">Chapter 9. 19 The DbMpoolFile Handle 20 </th> 21 </tr> 22 <tr> 23 <td width="20%" align="left"><a accesskey="p" href="logcompare.html">Prev</a> </td> 24 <th width="60%" align="center"> </th> 25 <td width="20%" align="right"> <a accesskey="n" href="dbget_mpf.html">Next</a></td> 26 </tr> 27 </table> 28 <hr /> 29 </div> 30 <div class="chapter" lang="en" xml:lang="en"> 31 <div class="titlepage"> 32 <div> 33 <div> 34 <h2 class="title"><a id="memp"></a>Chapter 9. 35 The DbMpoolFile Handle 36 </h2> 37 </div> 38 </div> 39 </div> 40 <pre class="programlisting">#include <db_cxx.h> 41 42class DbMpoolFile { 43public: 44 DB_MPOOLFILE *DbMpoolFile::get_DB_MPOOLFILE(); 45 const DB_MPOOLFILE *DbMpoolFile::get_const_DB_MPOOLFILE() const; ... 46}; </pre> 47 <p> 48 The memory pool interfaces for the Berkeley DB database environment are methods of the 49 <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle. The 50 <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> memory pool methods and the 51 <code class="classname">DB_MPOOLFILE</code> class provide general-purpose, page-oriented buffer 52 management of files. Although designed to work with the other 53 <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a>classes, they are also useful for more general 54 purposes. The memory pools are referred to in this document as simply 55 <span class="emphasis"><em>the cache</em></span>. 56 </p> 57 <p> 58 The cache may be shared between processes. The cache is usually filled by pages from one or 59 more files. Pages in the cache are replaced in LRU (least-recently-used) order, with each 60 new page replacing the page that has been unused the longest. Pages retrieved from the 61 cache using <a class="xref" href="mempfget.html" title="DbMpoolFile::get()">DbMpoolFile::get()</a> are 62 <span class="emphasis"><em>pinned</em></span> in the cache until they are returned to the control of the 63 cache using the <a class="xref" href="mempput.html" title="DbMpoolFile::put()">DbMpoolFile::put()</a> method. 64 </p> 65 <p> 66 The <code class="classname">DbMpoolFile</code> object is the handle for a file in the 67 cache. The handle is not free-threaded. Once the 68 <a class="xref" href="mempfclose.html" title="DbMpoolFile::close()">DbMpoolFile::close()</a> method is called, the handle 69 may not be accessed again, regardless of that method's return. 70 </p> 71 <div class="sect1" lang="en" xml:lang="en"> 72 <div class="titlepage"> 73 <div> 74 <div> 75 <h2 class="title" style="clear: both"><a id="memplist"></a>Memory Pools and Related Methods</h2> 76 </div> 77 </div> 78 </div> 79 <div class="navtable"> 80 <table border="1" width="80%"> 81 <thead> 82 <tr> 83 <th>Memory Pools and Related Methods</th> 84 <th>Description</th> 85 </tr> 86 </thead> 87 <tbody> 88 <tr> 89 <td> 90 <a class="xref" href="dbmemory.html" title="DbMemoryException">DbMemoryException</a> 91 </td> 92 <td>Exception class for insufficient memory</td> 93 </tr> 94 <tr> 95 <td> 96 <a class="xref" href="dbget_mpf.html" title="Db::get_mpf()">Db::get_mpf()</a> 97 </td> 98 <td>Return the DbMpoolFile for a Db</td> 99 </tr> 100 <tr> 101 <td> 102 <a class="xref" href="mempstat.html" title="DbEnv::memp_stat()">DbEnv::memp_stat()</a> 103 </td> 104 <td>Return cache statistics</td> 105 </tr> 106 <tr> 107 <td> 108 <a class="xref" href="mempstat_print.html" title="DbEnv::memp_stat_print()">DbEnv::memp_stat_print()</a> 109 </td> 110 <td>Print cache statistics</td> 111 </tr> 112 <tr> 113 <td> 114 <a class="xref" href="mempsync.html" title="DbEnv::memp_sync()">DbEnv::memp_sync()</a> 115 </td> 116 <td>Flush all pages from the cache</td> 117 </tr> 118 <tr> 119 <td> 120 <a class="xref" href="memptrickle.html" title="DbEnv::memp_trickle()">DbEnv::memp_trickle()</a> 121 </td> 122 <td>Flush some pages from the cache</td> 123 </tr> 124 <tr> 125 <td colspan="2"> 126 <span class="bold"> 127 <strong>Memory Pool Configuration</strong> 128 </span> 129 </td> 130 </tr> 131 <tr> 132 <td> 133 <a class="xref" href="mempregister.html" title="DbEnv::memp_register()">DbEnv::memp_register()</a> 134 </td> 135 <td>Register a custom file type</td> 136 </tr> 137 <tr> 138 <td><a class="xref" href="envset_cache_max.html" title="DbEnv::set_cache_max()">DbEnv::set_cache_max()</a>, <a class="xref" href="envget_cache_max.html" title="DbEnv::get_cache_max()">DbEnv::get_cache_max()</a></td> 139 <td>Set/get the maximum cache size</td> 140 </tr> 141 <tr> 142 <td><a class="xref" href="envset_cachesize.html" title="DbEnv::set_cachesize()">DbEnv::set_cachesize()</a>, <a class="xref" href="envget_cachesize.html" title="DbEnv::get_cachesize()">DbEnv::get_cachesize()</a></td> 143 <td>Set/get the environment cache size</td> 144 </tr> 145 <tr> 146 <td><a class="xref" href="mempset_mp_max_openfd.html" title="DbEnv::set_mp_max_openfd()">DbEnv::set_mp_max_openfd()</a>, <a class="xref" href="mempget_mp_max_openfd.html" title="DbEnv::get_mp_max_openfd()">DbEnv::get_mp_max_openfd()</a></td> 147 <td>Set/get the maximum number of open file descriptors</td> 148 </tr> 149 <tr> 150 <td><a class="xref" href="mempset_mp_max_write.html" title="DbEnv::set_mp_max_write()">DbEnv::set_mp_max_write()</a>, <a class="xref" href="mempget_mp_max_write.html" title="DbEnv::get_mp_max_write()">DbEnv::get_mp_max_write()</a></td> 151 <td>Set/get the maximum number of sequential disk writes</td> 152 </tr> 153 <tr> 154 <td><a class="xref" href="envset_mp_mmapsize.html" title="DbEnv::set_mp_mmapsize()">DbEnv::set_mp_mmapsize()</a>, <a class="xref" href="envget_mp_mmapsize.html" title="DbEnv::get_mp_mmapsize()">DbEnv::get_mp_mmapsize()</a></td> 155 <td>Set/get maximum file size to memory map when opened read-only</td> 156 </tr> 157 <tr> 158 <td colspan="2"> 159 <span class="bold"> 160 <strong>Memory Pool Files</strong> 161 </span> 162 </td> 163 </tr> 164 <tr> 165 <td> 166 <a class="xref" href="mempfcreate.html" title="DbEnv::memp_fcreate()">DbEnv::memp_fcreate()</a> 167 </td> 168 <td>Create a memory pool file handle</td> 169 </tr> 170 <tr> 171 <td> 172 <a class="xref" href="mempfclose.html" title="DbMpoolFile::close()">DbMpoolFile::close()</a> 173 </td> 174 <td>Close a file in the cache</td> 175 </tr> 176 <tr> 177 <td> 178 <a class="xref" href="mempfget.html" title="DbMpoolFile::get()">DbMpoolFile::get()</a> 179 </td> 180 <td>Get page from a file in the cache</td> 181 </tr> 182 <tr> 183 <td> 184 <a class="xref" href="mempfopen.html" title="DbMpoolFile::open()">DbMpoolFile::open()</a> 185 </td> 186 <td>Open a file in the cache</td> 187 </tr> 188 <tr> 189 <td> 190 <a class="xref" href="mempput.html" title="DbMpoolFile::put()">DbMpoolFile::put()</a> 191 </td> 192 <td>Return a page to the cache</td> 193 </tr> 194 <tr> 195 <td> 196 <a class="xref" href="mempfsync.html" title="DbMpoolFile::sync()">DbMpoolFile::sync()</a> 197 </td> 198 <td>Flush pages from a file from the cache</td> 199 </tr> 200 <tr> 201 <td colspan="2"> 202 <span class="bold"> 203 <strong>Memory Pool File Configuration</strong> 204 </span> 205 </td> 206 </tr> 207 <tr> 208 <td><a class="xref" href="mempset_clear_len.html" title="DbMpoolFile::set_clear_len()">DbMpoolFile::set_clear_len()</a>, <a class="xref" href="mempget_clear_len.html" title="DbMpoolFile::get_clear_len()">DbMpoolFile::get_clear_len()</a></td> 209 <td>Set/get number of bytes to clear when creating a new page</td> 210 </tr> 211 <tr> 212 <td><a class="xref" href="mempset_fileid.html" title="DbMpoolFile::set_fileid()">DbMpoolFile::set_fileid()</a>, <a class="xref" href="mempget_fileid.html" title="DbMpoolFile::get_fileid()">DbMpoolFile::get_fileid()</a></td> 213 <td>Set/get file unique identifier</td> 214 </tr> 215 <tr> 216 <td><a class="xref" href="mempset_flags.html" title="DbMpoolFile::set_flags()">DbMpoolFile::set_flags()</a>, <a class="xref" href="mempget_flags.html" title="DbMpoolFile::get_flags()">DbMpoolFile::get_flags()</a></td> 217 <td>Set/get file options</td> 218 </tr> 219 <tr> 220 <td><a class="xref" href="mempset_ftype.html" title="DbMpoolFile::set_ftype()">DbMpoolFile::set_ftype()</a>, <a class="xref" href="mempget_ftype.html" title="DbMpoolFile::get_ftype()">DbMpoolFile::get_ftype()</a></td> 221 <td>Set/get file type</td> 222 </tr> 223 <tr> 224 <td><a class="xref" href="mempset_lsn_offset.html" title="DbMpoolFile::set_lsn_offset()">DbMpoolFile::set_lsn_offset()</a>, <a class="xref" href="mempget_lsn_offset.html" title="DbMpoolFile::get_lsn_offset()">DbMpoolFile::get_lsn_offset()</a></td> 225 <td>Set/get file log-sequence-number offset</td> 226 </tr> 227 <tr> 228 <td><a class="xref" href="mempset_maxsize.html" title="DbMpoolFile::set_maxsize()">DbMpoolFile::set_maxsize()</a>, <a class="xref" href="mempget_maxsize.html" title="DbMpoolFile::get_maxsize()">DbMpoolFile::get_maxsize()</a></td> 229 <td>Set/get maximum file size</td> 230 </tr> 231 <tr> 232 <td><a class="xref" href="mempset_pgcookie.html" title="DbMpoolFile::set_pgcookie()">DbMpoolFile::set_pgcookie()</a>, <a class="xref" href="mempget_pgcookie.html" title="DbMpoolFile::get_pgcookie()">DbMpoolFile::get_pgcookie()</a></td> 233 <td>Set/get file cookie for pgin/pgout</td> 234 </tr> 235 <tr> 236 <td><a class="xref" href="mempset_priority.html" title="DbMpoolFile::set_priority()">DbMpoolFile::set_priority()</a>, <a class="xref" href="mempget_priority.html" title="DbMpoolFile::get_priority()">DbMpoolFile::get_priority()</a></td> 237 <td>Set/get cache file priority</td> 238 </tr> 239 </tbody> 240 </table> 241 </div> 242 </div> 243 </div> 244 <div class="navfooter"> 245 <hr /> 246 <table width="100%" summary="Navigation footer"> 247 <tr> 248 <td width="40%" align="left"><a accesskey="p" href="logcompare.html">Prev</a> </td> 249 <td width="20%" align="center"> </td> 250 <td width="40%" align="right"> <a accesskey="n" href="dbget_mpf.html">Next</a></td> 251 </tr> 252 <tr> 253 <td width="40%" align="left" valign="top">DbEnv::log_compare() </td> 254 <td width="20%" align="center"> 255 <a accesskey="h" href="index.html">Home</a> 256 </td> 257 <td width="40%" align="right" valign="top"> Db::get_mpf()</td> 258 </tr> 259 </table> 260 </div> 261 </body> 262</html> 263