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183 lines
7.5 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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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DbEnv::set_memory_max()</title>
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<link rel="up" href="env.html" title="Chapter 5. The DbEnv Handle" />
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<link rel="prev" href="envset_memory_init.html" title="DbEnv::set_memory_init()" />
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<p>Library Version 11.2.5.2</p>
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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_memory_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="envset_memory_init.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 5.
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The DbEnv Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="envset_message_stream.html">Next</a></td>
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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_memory_max"></a>DbEnv::set_memory_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_memory_max(roff_t size); </pre>
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<p>
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This method sets the maximum amount of memory to be used by shared
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structures in the main environment region. These are the
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structures used to coordinate access to the environment other than
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mutexes and those in the page cache (memory pool). If the region
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files are in memory mapped files, or if
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<code class="literal">DB_PRIVATE</code> is specified, the memory specified by
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this method is not allocated completely at startup. As memory is
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needed, the shared region will be extended or, in the case of
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<code class="literal">DB_PRIVATE</code>, more memory will be allocated using
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the system malloc call. For memory mapped files, a mapped region
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will be allocated to this size but the underlying file will only be
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allocated sufficient memory to hold the initial allocation of
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shared memory structures as set by
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<a class="xref" href="envset_memory_init.html" title="DbEnv::set_memory_init()">DbEnv::set_memory_init()</a>.
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</p>
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<p>
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If no memory maximum is specified then it is calculated from
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defaults, initial settings or (deprecated) maximum settings of the
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various shared structures. In the case of environments created
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with <code class="literal">DB_PRIVATE</code>, no maximum need be set and the
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shared structure allocation will grow as needed until the process
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memory limit is exhausted.
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</p>
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<p>
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The database environment's maximum memory may also be configured
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using the environment's
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<a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a>
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file. The syntax of the entry in that file is a single line with
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the string "set_memory_max", one or more whitespace characters,
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followed by the maximum to be allocated. Because the
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<a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a>
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file is read when the database environment is opened, it will
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silently overrule 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_memory_max()</code> method must be
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called prior to opening the database environment.
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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="id3605468"></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="id3605274"></a>size</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>size</strong></span> parameter
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identifies the maximum number of bytes to allocate.
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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="id3605673"></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_memory_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="id3606078"></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="id3606020"></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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</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="id3605632"></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="env.html#envlist" title="Database Environments and Related Methods">Database Environments 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="envset_memory_init.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="env.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="envset_message_stream.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::set_memory_init() </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_message_stream()</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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