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>Db::set_priority()</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="db.html" title="Chapter 2. The Db Handle" /> 11 <link rel="prev" href="dbset_partition_dirs.html" title="Db::set_partition_dirs()" /> 12 <link rel="next" href="dbset_q_extentsize.html" title="Db::set_q_extentsize()" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">Db::set_priority()</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="dbset_partition_dirs.html">Prev</a> </td> 22 <th width="60%" align="center">Chapter 2. 23 The Db Handle 24 </th> 25 <td width="20%" align="right"> <a accesskey="n" href="dbset_q_extentsize.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="dbset_priority"></a>Db::set_priority()</h2> 35 </div> 36 </div> 37 </div> 38 <pre class="programlisting">#include <db_cxx.h> 39 40int 41Db::set_priority(DB_CACHE_PRIORITY priority); </pre> 42 <p> 43 Set the cache priority for pages referenced by the 44 <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> handle. 45 </p> 46 <p> 47 The priority of a page biases the replacement algorithm to be more or 48 less likely to discard a page when space is needed in the buffer pool. 49 The bias is temporary, and pages will eventually be discarded if they 50 are not referenced again. The <code class="methodname">Db::set_priority()</code> method is only 51 advisory, and does not guarantee pages will be treated in a specific 52 way. 53 </p> 54 <p> 55 The <code class="methodname">Db::set_priority()</code> method may be called at any time during the 56 life of the application. 57 </p> 58 <p> 59 The <code class="methodname">Db::set_priority()</code> <span> 60 61 <span> 62 method either returns a non-zero error value or throws an 63 exception that encapsulates a non-zero error value on 64 failure, and returns 0 on success. 65 </span> 66 </span> 67 </p> 68 <div class="sect2" lang="en" xml:lang="en"> 69 <div class="titlepage"> 70 <div> 71 <div> 72 <h3 class="title"><a id="id1650160"></a>Parameters</h3> 73 </div> 74 </div> 75 </div> 76 <div class="sect3" lang="en" xml:lang="en"> 77 <div class="titlepage"> 78 <div> 79 <div> 80 <h4 class="title"><a id="id1650481"></a>priority</h4> 81 </div> 82 </div> 83 </div> 84 <p> 85 The <span class="bold"><strong>priority</strong></span> parameter must be set to 86 one of the following values: 87 </p> 88 <div class="itemizedlist"> 89 <ul type="disc"> 90 <li> 91 <p><a id="set_priority_DB_PRIORITY_VERY_LOW"></a> 92 <code class="literal">DB_PRIORITY_VERY_LOW</code> 93 </p> 94 <p> 95 The lowest priority: pages are the most likely to be discarded. 96 </p> 97 </li> 98 <li> 99 <p><a id="set_priority_DB_PRIORITY_LOW"></a> 100 <code class="literal">DB_PRIORITY_LOW</code> 101 </p> 102 <p> 103 The next lowest priority. 104 </p> 105 </li> 106 <li> 107 <p><a id="set_priority_DB_PRIORITY_DEFAULT"></a> 108 <code class="literal">DB_PRIORITY_DEFAULT</code> 109 </p> 110 <p> 111 The default priority. 112 </p> 113 </li> 114 <li> 115 <p><a id="set_priority_DB_PRIORITY_HIGH"></a> 116 <code class="literal">DB_PRIORITY_HIGH</code> 117 </p> 118 <p> 119 The next highest priority. 120 </p> 121 </li> 122 <li> 123 <p><a id="set_priority_DB_PRIORITY_VERY_HIGH"></a> 124 <code class="literal">DB_PRIORITY_VERY_HIGH</code> 125 </p> 126 <p> 127 The highest priority: pages are the least likely to be discarded. 128 </p> 129 </li> 130 </ul> 131 </div> 132 </div> 133 </div> 134 <div class="sect2" lang="en" xml:lang="en"> 135 <div class="titlepage"> 136 <div> 137 <div> 138 <h3 class="title"><a id="id1650161"></a>Class</h3> 139 </div> 140 </div> 141 </div> 142 <p> 143 <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> 144 </p> 145 </div> 146 <div class="sect2" lang="en" xml:lang="en"> 147 <div class="titlepage"> 148 <div> 149 <div> 150 <h3 class="title"><a id="id1650191"></a>See Also</h3> 151 </div> 152 </div> 153 </div> 154 <p> 155 <a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a> 156 </p> 157 </div> 158 </div> 159 <div class="navfooter"> 160 <hr /> 161 <table width="100%" summary="Navigation footer"> 162 <tr> 163 <td width="40%" align="left"><a accesskey="p" href="dbset_partition_dirs.html">Prev</a> </td> 164 <td width="20%" align="center"> 165 <a accesskey="u" href="db.html">Up</a> 166 </td> 167 <td width="40%" align="right"> <a accesskey="n" href="dbset_q_extentsize.html">Next</a></td> 168 </tr> 169 <tr> 170 <td width="40%" align="left" valign="top">Db::set_partition_dirs() </td> 171 <td width="20%" align="center"> 172 <a accesskey="h" href="index.html">Home</a> 173 </td> 174 <td width="40%" align="right" valign="top"> Db::set_q_extentsize()</td> 175 </tr> 176 </table> 177 </div> 178 </body> 179</html> 180