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273 lines
12 KiB
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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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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DbEnv::set_memory_init()</title>
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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="env.html" title="Chapter 5. The DbEnv Handle" />
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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_memory_init()</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_isalive.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_memory_max.html">Next</a></td>
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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_memory_init"></a>DbEnv::set_memory_init()</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_init(DB_MEM_CONFIG object, u_int32_t count); </pre>
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<p>
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This method sets the number of objects to allocate and initialize
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for a specified structure when an environment is created. Doing
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this helps avoid memory contention after startup. Using this
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method is optional; failure to use this method causes BDB to
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allocate a minimal number of structures that will grow dynamically.
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These structures are all allocated from the main environment
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region. The amount of memory in this region can be set via the
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<a class="xref" href="envset_memory_max.html" title="DbEnv::set_memory_max()">DbEnv::set_memory_max()</a>
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method. If this method is not called then memory will be limited
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to the initial settings or by the (deprecated) set maximum
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interfaces.
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</p>
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<p>
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The database environment's initialization may also be configured
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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
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in that file is a single line with the string "set_memory_init",
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one or more whitespace characters, followed by the struct
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specification, more white space and the count to be allocated.
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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
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is opened, it will silently overrule configuration done before
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that time.
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</p>
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<p>
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The <code class="methodname">DbEnv::set_memory_init()</code> method must
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be called prior to opening the database environment. It may be
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called as often as needed to set the different configurations.
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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="id3622953"></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="id3625261"></a>struct</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>struct</strong></span> parameter must be
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set to one of the following:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p><a id="envmem_DB_MEM_LOCK"></a>
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<code class="literal">DB_MEM_LOCK</code>
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</p>
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<p>
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Initialize locks. A thread uses this structure
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to lock a page (or record for the QUEUE access
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method) and hold it to the end of a transactions.
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</p>
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</li>
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<li>
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<p><a id="envmem_DB_MEM_LOCKOBJECT"></a>
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<code class="literal">DB_MEM_LOCKOBJECT</code>
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</p>
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<p>
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Initialize lock objects. For each page (or record) which
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is locked in the system, a lock object will be allocated.
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</p>
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</li>
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<li>
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<p><a id="envmem_DB_MEM_LOCKER"></a>
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<code class="literal">DB_MEM_LOCKER</code>
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</p>
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<p>
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Initialize lockers. Each thread which is active in a
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transactional environment will use a locker structure
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either for each transaction which is active, or for each
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non-transactional cursor that is active.
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</p>
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</li>
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<li>
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<p><a id="envmem_DB_MEM_LOGID"></a>
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<code class="literal">DB_MEM_LOGID</code>
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</p>
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<p>
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Initialize the log fileid structures. For each database handle
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which is opened for writing in a transactional environment,
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a log fileid structure is used.
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</p>
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</li>
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<li>
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<p><a id="envmem_DB_MEM_TRANSACTION"></a>
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<code class="literal">DB_MEM_TRANSACTION</code>
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</p>
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<p>
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Initialize transaction structures. Each active
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transaction uses a transaction structure until it
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either commits or aborts.
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</p>
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<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
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<h3 class="title">Note</h3>
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<p>
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Currently transaction structures are not
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preallocated. This setting will be used to
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preallocate memory and objects related to
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transactions such as locker structures and
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mutexes.
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</p>
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</div>
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</li>
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<li>
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<p><a id="envmem_DB_MEM_THREAD"></a>
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<code class="literal">DB_MEM_THREAD</code>
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</p>
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<p>
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Initialize thread identification structures. If thread
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tracking is enabled then each active thread will use a
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structure. Note that since a thread does not signal the
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BDB library that it will no longer be making calls, unused
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structures may accumulate until a cleanup is triggered either
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using a high water mark or by running
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<a class="xref" href="envfailchk.html" title="DbEnv::failchk()">DbEnv::failchk()</a>.
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</p>
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</li>
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</ul>
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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="id3625141"></a>count</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>count</strong></span> parameter
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sets the number of specified objects to initialize.
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</p>
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<p>
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The <span class="bold"><strong>count</strong></span> specified for
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locks and lock objects should be at least 5 times the
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number of lock table partitions. You can examine the
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current number of lock table partitions configured for your
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environment using the
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<a class="xref" href="envget_lk_partitions.html" title="DbEnv::get_lk_partitions()">DbEnv::get_lk_partitions()</a>
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method.
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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="id3624922"></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_init()</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="id3624834"></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="id3624909"></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="id3625361"></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_isalive.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_memory_max.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_isalive() </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_memory_max()</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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