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<th colspan="3" align="center">DbEnv::set_memory_init()</th>
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<div class="sect1" lang="en" xml:lang="en">
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<div>
<h2 class="title" style="clear: both"><a id="envset_memory_init"></a>DbEnv::set_memory_init()</h2>
</div>
</div>
</div>
<pre class="programlisting">#include <db_cxx.h>
int
DbEnv::set_memory_init(DB_MEM_CONFIG type, u_int32_t count); </pre>
<p>
This method sets the number of objects to allocate and initialize
for a specified structure when an environment is created. Doing
this helps avoid memory contention after startup. Using this
method is optional; failure to use this method causes BDB to
allocate a minimal number of structures that will grow dynamically.
These structures are all allocated from the main environment
region. The amount of memory in this region can be set via the
<a class="xref" href="envset_memory_max.html" title="DbEnv::set_memory_max()">DbEnv::set_memory_max()</a>
method. If this method is not called then memory will be limited
to the initial settings or by the (deprecated) set maximum
interfaces.
</p>
<p>
The database environment's initialization 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_memory_init",
one or more whitespace characters, followed by the struct
specification, more white space and the count to be allocated.
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_memory_init()</code> method must
be called prior to opening the database environment. It may be
called as often as needed to set the different configurations.
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp7518408"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp7515648"></a>type</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>type</strong></span> parameter must be
set to one of the following:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p><a id="envmem_DB_MEM_LOCK"></a>
<code class="literal">DB_MEM_LOCK</code>
</p>
<p>
Initialize locks. A thread uses this structure
to lock a page (or record for the QUEUE access
method) and hold it to the end of a transactions.
</p>
</li>
<li>
<p><a id="envmem_DB_MEM_LOCKOBJECT"></a>
<code class="literal">DB_MEM_LOCKOBJECT</code>
</p>
<p>
Initialize lock objects. For each page (or record) which
is locked in the system, a lock object will be allocated.
</p>
</li>
<li>
<p><a id="envmem_DB_MEM_LOCKER"></a>
<code class="literal">DB_MEM_LOCKER</code>
</p>
<p>
Initialize lockers. Each thread which is active in a
transactional environment will use a locker structure
either for each transaction which is active, or for each
non-transactional cursor that is active.
</p>
</li>
<li>
<p><a id="envmem_DB_MEM_LOGID"></a>
<code class="literal">DB_MEM_LOGID</code>
</p>
<p>
Initialize the log fileid structures. For each database handle
which is opened for writing in a transactional environment,
a log fileid structure is used.
</p>
</li>
<li>
<p><a id="envmem_DB_MEM_TRANSACTION"></a>
<code class="literal">DB_MEM_TRANSACTION</code>
</p>
<p>
Initialize transaction structures. Each active
transaction uses a transaction structure until it
either commits or aborts.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>
Currently transaction structures are not
preallocated. This setting will be used to
preallocate memory and objects related to
transactions such as locker structures and
mutexes.
</p>
</div>
</li>
<li>
<p><a id="envmem_DB_MEM_THREAD"></a>
<code class="literal">DB_MEM_THREAD</code>
</p>
<p>
Initialize thread identification structures. If thread
tracking is enabled then each active thread will use a
structure. Note that since a thread does not signal the
BDB library that it will no longer be making calls, unused
structures may accumulate until a cleanup is triggered either
using a high water mark or by running
<a class="xref" href="envfailchk.html" title="DbEnv::failchk()">DbEnv::failchk()</a>.
</p>
</li>
</ul>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp7521336"></a>count</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>count</strong></span> parameter
sets the number of specified objects to initialize.
</p>
<p>
The <span class="bold"><strong>count</strong></span> specified for
locks and lock objects should be at least 5 times the
number of lock table partitions. You can examine the
current number of lock table partitions configured for your
environment using the
<a class="xref" href="envget_lk_partitions.html" title="DbEnv::get_lk_partitions()">DbEnv::get_lk_partitions()</a>
method.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp7482376"></a>Errors</h3>
</div>
</div>
</div>
<p>
The <code class="methodname">DbEnv::set_memory_init()</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="idp7487224"></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="idp7512336"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp7499728"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a class="xref" href="env.html#envlist" title="Database Environments and Related Methods">Database Environments and Related Methods</a>
</p>
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