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<h2 class="title" style="clear: both"><a id="envset_backup_config"></a>DbEnv::set_backup_config()</h2>
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<pre class="programlisting">#include <db_cxx.h>
DB_ENV->set_backup_config(db_backup_config_t option, u_int32_t value);</pre>
<p>
The <code class="methodname">DbEnv::set_backup_config()</code> method
configures tuning parameters for the hot backup APIs. See the
<a class="xref" href="envbackup.html" title="DbEnv::backup()">DbEnv::backup()</a>
and
<a class="xref" href="envdbbackup.html" title="DbEnv::dbbackup()">DbEnv::dbbackup()</a>
methods for a description of the hot backup APIs.
</p>
<p>
The <code class="methodname">DbEnv::set_backup_config()</code> method
configures operations performed using the specified
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle, not all operations
performed on the underlying database environment.
</p>
<p>
The <code class="methodname">DbEnv::set_backup_config()</code> method may
be called at any time during the life of the application.
</p>
<p>
The <code class="methodname">DbEnv::set_backup_config()</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>
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<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
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<div>
<h3 class="title"><a id="idp7152992"></a>Parameters</h3>
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<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp7194016"></a>option</h4>
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<p>
The <span class="bold"><strong>option</strong></span> parameter
identifies the backup parameter to be modified. It
must be one of the following:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<code class="literal">DB_BACKUP_WRITE_DIRECT</code>
</p>
<p>
Turning this on causes direct I/O to be used when
writing pages to the disk. For some environments,
direct I/O can provide faster write throughput, but
usually it is slower because the OS buffer pool
offers asynchronous activity.
</p>
<p>
By default, this option is turned off.
</p>
</li>
<li>
<p>
<code class="literal">DB_BACKUP_READ_COUNT</code>
</p>
<p>
Configures the number of pages to read before
pausing. Increasing this value increases the amount
of I/O the backup process performs for any given
time interval. If your application is already
heavily I/O bound, setting this value to a lower
number may help to improve your overall data
throughput by reducing the I/O demands placed on
your system.
</p>
<p>
By default, all pages are read without a pause.
</p>
</li>
<li>
<p>
<code class="literal">DB_BACKUP_READ_SLEEP</code>
</p>
<p>
Configures the number of microseconds to sleep
between batches of reads. Increasing this value
decreases the amount of I/O the backup process
performs for any given time interval. If your
application is already heavily I/O bound, setting
this value to a higher number may help to improve
your overall data throughput by reducing the I/O
demands placed on your system.
</p>
</li>
<li>
<p>
<code class="literal">DB_BACKUP_SIZE</code>
</p>
<p>
Configures the size of the buffer, in bytes, to
read from the database. Default is 1 megabyte.
</p>
</li>
</ul>
</div>
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<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp7206960"></a>value</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>value</strong></span> parameter sets
the configuration value for the option identified by the
<span class="bold"><strong>option</strong></span> parameter. For
those options which can only be turned on or off, this
parameter should be set to <code class="literal">0</code>
for off and <code class="literal">1</code> for on. Otherwise, set
this parameter to an integer value that represents the
number of units for which you are configuring the backup
APIs.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp7188040"></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="idp7209120"></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>,
<a class="xref" href="envget_backup_config.html" title="DbEnv::get_backup_config()">DbEnv::get_backup_config()</a>,
<a class="xref" href="envbackup.html" title="DbEnv::backup()">DbEnv::backup()</a>,
<a class="xref" href="envdbbackup.html" title="DbEnv::dbbackup()">DbEnv::dbbackup()</a>
</p>
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