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<h2 class="title" style="clear: both"><a id="envset_memory_init"></a>
<span>DbEnv::set_memory_init()</span>
</h2>
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<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()">
<span>DbEnv::set_memory_max()</span>
</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="idm139755615006480"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idm139755614954672"></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_DATABASE"></a>
<code class="literal">DB_MEM_DATABASE</code>
</p>
<p>
Initialize the number of databases in the
environment. This should include each on-disk
database and each named in-memory database. If
using replication, use the same value on all sites
in the replication group.
</p>
</li>
<li>
<p><a id="envmem_DB_MEM_DATABASE_LENGTH"></a>
<code class="literal">DB_MEM_DATABASE_LENGTH</code>
</p>
<p>
Initialize the maximum combined length of a database's
directory and name strings. For an on-disk database,
the database name is the
<span class="bold"><strong>file</strong></span> parameter to the
<a class="xref" href="envopen.html" title="DbEnv::open()">
<span>DbEnv::open()</span>
</a>
method. For a named in-memory database, the database
name is the
<span class="bold"><strong>database</strong></span> parameter
to the
<a class="xref" href="envopen.html" title="DbEnv::open()">
<span>DbEnv::open()</span>
</a>
method. If using replication, use the same value on
all sites in the replication group.
</p>
</li>
<li>
<p><a id="envmem_DB_MEM_EXTFILE_DATABASE"></a>
<code class="literal">DB_MEM_EXTFILE_DATABASE</code>
</p>
<p>
Initialize the number of database files and
subdatabases using external files. This value should
include the number of database files that use
external files but do not contain subdatabases.
This value should also include the number of
subdatabases that use external files. It should
be set in addition to the
<code class="literal">DB_MEM_DATABASE</code> value. If using
replication, use the same value on all sites in
the replication group.
</p>
<p>
Here are some examples of database files with different
characteristics and how each database file should
affect these values:
</p>
<div class="itemizedlist">
<ul type="circle">
<li>
Not using external files, no subdatabases:
add 1 to <code class="literal">DB_MEM_DATABASE</code>.
</li>
<li>
Not using external files, three subdatabases:
add 1 to <code class="literal">DB_MEM_DATABASE</code>.
</li>
<li>
Using external files, no subdatabases:
add 1 to <code class="literal">DB_MEM_DATABASE</code>
and add 1 to
<code class="literal">DB_MEM_EXTFILE_DATABASE</code>.
</li>
<li>
Using external files, three subdatabases:
add 1 to <code class="literal">DB_MEM_DATABASE</code>
and add 3 to
<code class="literal">DB_MEM_EXTFILE_DATABASE</code>.
</li>
</ul>
</div>
</li>
<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 transaction.
</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_REP_SITE"></a>
<code class="literal">DB_MEM_REP_SITE</code>
</p>
<p>
If using replication, initialize the maximum number
of sites in the replication group. Use the same
value on all sites in the replication group.
</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()">
<span>DbEnv::failchk()</span>
</a>.
</p>
</li>
</ul>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idm139755614663312"></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()">
<span>DbEnv::get_lk_partitions()</span>
</a>
method.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idm139755614661232"></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="idm139755614667056"></a>EINVAL</h4>
</div>
</div>
</div>
<p>
If the method was called after <a class="xref" href="envopen.html" title="DbEnv::open()">
<span>DbEnv::open()</span>
</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="idm139755614717872"></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="idm139755614717408"></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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