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200 lines
8.4 KiB
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DbEnv::set_tx_max()</title>
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<link rel="stylesheet" href="apiReference.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB C++ API Reference" />
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<link rel="up" href="txn.html" title="Chapter 13. The DbTxn Handle" />
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<link rel="prev" href="envget_tx_timestamp.html" title="DbEnv::get_tx_timestamp()" />
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<link rel="next" href="envset_tx_timestamp.html" title="DbEnv::set_tx_timestamp()" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 11.2.5.2</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">DbEnv::set_tx_max()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="envget_tx_timestamp.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 13.
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The DbTxn Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="envset_tx_timestamp.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="envset_tx_max"></a>DbEnv::set_tx_max()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db_cxx.h>
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int
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DbEnv::set_tx_max(u_int32_t max); </pre>
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<p>
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Configure the Berkeley DB database environment to support at least
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<span class="bold"><strong>max</strong></span> active transactions. This value
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bounds the size of the memory allocated for transactions. Child
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transactions are counted as active until they either commit or abort.
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</p>
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<p>
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Transactions that update multiversion databases are not freed until
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the last page version that the transaction created is flushed from
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cache. This means that applications using multi-version concurrency
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control may need a transaction for each page in cache, in the extreme
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case.
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</p>
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<p>
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When all of the memory available in the database environment for
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transactions is in use, calls to
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<a class="xref" href="txnbegin.html" title="DbEnv::txn_begin()">DbEnv::txn_begin()</a> will fail
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(until some active transactions complete). If
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<code class="classname">DbEnv::set_tx_max()</code> is never called,
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the database environment is configured to support at least 100
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active transactions.
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</p>
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<p>
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The database environment's number of active transactions may also
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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
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of the entry in that file is a single line with the string
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"set_tx_max", one or more whitespace characters, and the number of
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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
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database environment is opened, it will silently overrule
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configuration done before that time.
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</p>
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<p>
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The <code class="methodname">DbEnv::set_tx_max()</code> method configures
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a database environment, not only operations performed using the
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specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle.
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</p>
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<p>
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The <code class="methodname">DbEnv::set_tx_max()</code> method may not be called after the
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<a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method is called.
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If the database environment already exists when
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<a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> is called, the
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information specified to <code class="methodname">DbEnv::set_tx_max()</code> will be ignored.
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</p>
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<p>
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The <code class="methodname">DbEnv::set_tx_max()</code> <span>
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<span>
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method either returns a non-zero error value or throws an
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exception that encapsulates a non-zero error value on
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failure, and returns 0 on success.
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</span>
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</span>
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</p>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3670813"></a>Parameters</h3>
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</div>
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</div>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3670802"></a>max</h4>
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>max</strong></span> parameter configures the
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minimum number of simultaneously active transactions supported by
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Berkeley DB database environment.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3670367"></a>Errors</h3>
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</div>
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</div>
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</div>
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<p>
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The <code class="methodname">DbEnv::set_tx_max()</code> <span>
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<span>
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method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
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exception, encapsulating one of the following non-zero errors, or return one
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of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3671032"></a>EINVAL</h4>
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</div>
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</div>
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</div>
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<p>
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If the method was called after <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a>
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was called; or if an invalid flag value or parameter was specified.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3671055"></a>Class</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>,
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<a class="link" href="txn.html" title="Chapter 13. The DbTxn Handle">DbTxn</a>
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</p>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3671042"></a>See Also</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="xref" href="txn.html#txnlist" title="Transaction Subsystem and Related Methods">Transaction Subsystem and Related Methods</a>
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</p>
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</div>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="envget_tx_timestamp.html">Prev</a> </td>
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|||
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<td width="20%" align="center">
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<a accesskey="u" href="txn.html">Up</a>
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</td>
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|||
|
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<td width="40%" align="right"> <a accesskey="n" href="envset_tx_timestamp.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">DbEnv::get_tx_timestamp() </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> DbEnv::set_tx_timestamp()</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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