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Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
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<p>Library Version 11.2.5.2</p>
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<th colspan="3" align="center">DbEnv::set_tx_max()</th>
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<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
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<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
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<div>
<h2 class="title" style="clear: both"><a id="envset_tx_max"></a>DbEnv::set_tx_max()</h2>
</div>
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</div>
<pre class="programlisting">#include &lt;db_cxx.h&gt;
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>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h3 class="title"><a id="id3651330"></a>Parameters</h3>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3651320"></a>max</h4>
Release 5.2.28 on 6/10/2011
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</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>
Release 5.2.36 on 9/14/2022
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<h3 class="title"><a id="id3651216"></a>Errors</h3>
Release 5.2.28 on 6/10/2011
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</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>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3651557"></a>EINVAL</h4>
Release 5.2.28 on 6/10/2011
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</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>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h3 class="title"><a id="id3651579"></a>Class</h3>
Release 5.2.28 on 6/10/2011
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</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>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h3 class="title"><a id="id3651566"></a>See Also</h3>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
<a class="xref" href="txn.html#txnlist" title="Transaction Subsystem and Related Methods">Transaction Subsystem and Related Methods</a>
</p>
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