<?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_tx_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="txn.html" title="Chapter 13. The DbTxn Handle" /> <link rel="prev" href="envget_tx_timestamp.html" title="DbEnv::get_tx_timestamp()" /> <link rel="next" href="envset_tx_timestamp.html" title="DbEnv::set_tx_timestamp()" /> </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_tx_max()</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="envget_tx_timestamp.html">Prev</a> </td> <th width="60%" align="center">Chapter 13. The DbTxn Handle </th> <td width="20%" align="right"> <a accesskey="n" href="envset_tx_timestamp.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_tx_max"></a>DbEnv::set_tx_max()</h2> </div> </div> </div> <pre class="programlisting">#include <db_cxx.h> int DbEnv::set_tx_max(u_int32_t max); </pre> <p> Configure the Berkeley DB database environment to support at least <span class="bold"><strong>max</strong></span> active transactions. This value bounds the size of the memory allocated for transactions. Child transactions are counted as active until they either commit or abort. </p> <p> Transactions that update multiversion databases are not freed until the last page version that the transaction created is flushed from cache. This means that applications using multi-version concurrency control may need a transaction for each page in cache, in the extreme case. </p> <p> When all of the memory available in the database environment for transactions is in use, calls to <a class="xref" href="txnbegin.html" title="DbEnv::txn_begin()">DbEnv::txn_begin()</a> will fail (until some active transactions complete). If <code class="classname">DbEnv::set_tx_max()</code> is never called, the database environment is configured to support at least 100 active transactions. </p> <p> The database environment's number of active transactions 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_tx_max", one or more whitespace characters, and the number of transactions. 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_tx_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::set_tx_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::set_tx_max()</code> will be ignored. </p> <p> The <code class="methodname">DbEnv::set_tx_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="idp4905952"></a>Parameters</h3> </div> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp4905304"></a>max</h4> </div> </div> </div> <p> The <span class="bold"><strong>max</strong></span> parameter configures the minimum number of simultaneously active transactions supported by Berkeley DB database environment. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp4884328"></a>Errors</h3> </div> </div> </div> <p> The <code class="methodname">DbEnv::set_tx_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="idp4919800"></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="idp4921128"></a>Class</h3> </div> </div> </div> <p> <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>, <a class="link" href="txn.html" title="Chapter 13. The DbTxn Handle">DbTxn</a> </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp4906816"></a>See Also</h3> </div> </div> </div> <p> <a class="xref" href="txn.html#txnlist" title="Transaction Subsystem and Related Methods">Transaction Subsystem 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="envget_tx_timestamp.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="txn.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="envset_tx_timestamp.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">DbEnv::get_tx_timestamp() </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> DbEnv::set_tx_timestamp()</td> </tr> </table> </div> </body> </html>