<?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::set_memory_init()</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="env.html" title="Chapter 5. The DbEnv Handle" /> <link rel="prev" href="envset_isalive.html" title="DbEnv::set_isalive()" /> <link rel="next" href="envset_memory_max.html" title="DbEnv::set_memory_max()" /> </head> <body> <div xmlns="" class="navheader"> <div class="libver"> <p>Library Version 11.2.5.3</p> </div> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">DbEnv::set_memory_init()</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="envset_isalive.html">Prev</a> </td> <th width="60%" align="center">Chapter 5. The DbEnv Handle </th> <td width="20%" align="right"> <a accesskey="n" href="envset_memory_max.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="envset_memory_init"></a>DbEnv::set_memory_init()</h2> </div> </div> </div> <pre class="programlisting">#include <db_cxx.h> int DbEnv::set_memory_init(DB_MEM_CONFIG type, u_int32_t count); </pre> <p> This method sets the number of objects to allocate and initialize for a specified structure when an environment is created. Doing this helps avoid memory contention after startup. Using this method is optional; failure to use this method causes BDB to allocate a minimal number of structures that will grow dynamically. These structures are all allocated from the main environment region. The amount of memory in this region can be set via the <a class="xref" href="envset_memory_max.html" title="DbEnv::set_memory_max()">DbEnv::set_memory_max()</a> method. If this method is not called then memory will be limited to the initial settings or by the (deprecated) set maximum interfaces. </p> <p> The database environment's initialization 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 "set_memory_init", one or more whitespace characters, followed by the struct specification, more white space and the count to be allocated. 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::set_memory_init()</code> method must be called prior to opening the database environment. It may be called as often as needed to set the different configurations. </p> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp7518408"></a>Parameters</h3> </div> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp7515648"></a>type</h4> </div> </div> </div> <p> The <span class="bold"><strong>type</strong></span> parameter must be set to one of the following: </p> <div class="itemizedlist"> <ul type="disc"> <li> <p><a id="envmem_DB_MEM_LOCK"></a> <code class="literal">DB_MEM_LOCK</code> </p> <p> Initialize locks. A thread uses this structure to lock a page (or record for the QUEUE access method) and hold it to the end of a transactions. </p> </li> <li> <p><a id="envmem_DB_MEM_LOCKOBJECT"></a> <code class="literal">DB_MEM_LOCKOBJECT</code> </p> <p> Initialize lock objects. For each page (or record) which is locked in the system, a lock object will be allocated. </p> </li> <li> <p><a id="envmem_DB_MEM_LOCKER"></a> <code class="literal">DB_MEM_LOCKER</code> </p> <p> Initialize lockers. Each thread which is active in a transactional environment will use a locker structure either for each transaction which is active, or for each non-transactional cursor that is active. </p> </li> <li> <p><a id="envmem_DB_MEM_LOGID"></a> <code class="literal">DB_MEM_LOGID</code> </p> <p> Initialize the log fileid structures. For each database handle which is opened for writing in a transactional environment, a log fileid structure is used. </p> </li> <li> <p><a id="envmem_DB_MEM_TRANSACTION"></a> <code class="literal">DB_MEM_TRANSACTION</code> </p> <p> Initialize transaction structures. Each active transaction uses a transaction structure until it either commits or aborts. </p> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <h3 class="title">Note</h3> <p> Currently transaction structures are not preallocated. This setting will be used to preallocate memory and objects related to transactions such as locker structures and mutexes. </p> </div> </li> <li> <p><a id="envmem_DB_MEM_THREAD"></a> <code class="literal">DB_MEM_THREAD</code> </p> <p> Initialize thread identification structures. If thread tracking is enabled then each active thread will use a structure. Note that since a thread does not signal the BDB library that it will no longer be making calls, unused structures may accumulate until a cleanup is triggered either using a high water mark or by running <a class="xref" href="envfailchk.html" title="DbEnv::failchk()">DbEnv::failchk()</a>. </p> </li> </ul> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp7521336"></a>count</h4> </div> </div> </div> <p> The <span class="bold"><strong>count</strong></span> parameter sets the number of specified objects to initialize. </p> <p> The <span class="bold"><strong>count</strong></span> specified for locks and lock objects should be at least 5 times the number of lock table partitions. You can examine the current number of lock table partitions configured for your environment using the <a class="xref" href="envget_lk_partitions.html" title="DbEnv::get_lk_partitions()">DbEnv::get_lk_partitions()</a> method. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp7482376"></a>Errors</h3> </div> </div> </div> <p> The <code class="methodname">DbEnv::set_memory_init()</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="idp7487224"></a>EINVAL</h4> </div> </div> </div> <p> If the method was called after <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> was called; or if 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="idp7512336"></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="idp7499728"></a>See Also</h3> </div> </div> </div> <p> <a class="xref" href="env.html#envlist" title="Database Environments and Related Methods">Database Environments and Related 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="envset_isalive.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="env.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="envset_memory_max.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">DbEnv::set_isalive() </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> DbEnv::set_memory_max()</td> </tr> </table> </div> </body> </html>