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<div class="sect1" lang="en" xml:lang="en">
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<h2 class="title" style="clear: both"><a id="envset_backup_callbacks"></a>DB_ENV->set_backup_callbacks()</h2>
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<pre class="programlisting">#include <db.h>
DB_ENV->set_backup_callbacks(DB_ENV,
int (*open_func)(DB_ENV *, const char *dbname,
const char *target, void **handle),
int (*write_func)(DB_ENV *, u_int32_t offset_gbytes,
u_int32_t offset_bytes, u_int32_t size,
u_int8_t *buf, void *handle),
int (*close_func)(DB_ENV *, const char *dbname, void *handle)); </pre>
<p>
The <code class="methodname">DB_ENV->set_backup_callbacks()</code> method
configures three callback functions which can be used by the
<a class="xref" href="envbackup.html" title="DB_ENV->backup()">DB_ENV->backup()</a>
or
<a class="xref" href="envdbbackup.html" title="DB_ENV->dbbackup()">DB_ENV->dbbackup()</a>
methods to override their default behavior. If one callback is
configured, then all three callbacks must be configured.
These callbacks are required if the <code class="literal">target</code> parameter is
set to <code class="literal">NULL</code> for the
<a class="xref" href="envbackup.html" title="DB_ENV->backup()">DB_ENV->backup()</a>
or
<a class="xref" href="envdbbackup.html" title="DB_ENV->dbbackup()">DB_ENV->dbbackup()</a>
methods.
</p>
<p>
The <code class="methodname">DB_ENV->set_backup_callbacks()</code> method
configures operations performed using the specified
<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> handle, not all operations
performed on the underlying database environment.
</p>
<p>
The <code class="methodname">DB_ENV->set_backup_callbacks()</code> method may
be called at any time during the life of the application.
</p>
<p>
The <code class="methodname">DB_ENV->set_backup_callbacks()</code> <span>
<span>
method returns a non-zero error value on failure and 0 on success.
</span>
</span>
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp51828904"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp51800216"></a>open_func</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>open_func</strong></span> parameter
is the function used when a target location is opened
during a backup. This function should do whatever is
necessary to prepare the backup destination for
writing the data.
</p>
<p>
This function takes four parameters:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<code class="literal">dbenv</code>
</p>
<p>
The <span class="bold"><strong>dbenv</strong></span>
parameter is the enclosing database environment
handle.
</p>
</li>
<li>
<p>
<code class="literal">dbname</code>
</p>
<p>
The <span class="bold"><strong>dbname</strong></span> parameter is the
name of the database being backed up.
</p>
</li>
<li>
<p>
<code class="literal">target</code>
</p>
<p>
The <span class="bold"><strong>target</strong></span> parameter is the
backup's directory destination.
</p>
</li>
<li>
<p>
<code class="literal">handle</code>
</p>
<p>
The <span class="bold"><strong>handle</strong></span> parameter references
the handle (usually a file handle) to which the backup will be
written.
</p>
</li>
</ul>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp51798280"></a>write_func</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>write_func</strong></span> parameter
is the function used to write data during a backup.
The function takes six parameters:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<code class="literal">dbenv</code>
</p>
<p>
The <span class="bold"><strong>dbenv</strong></span>
parameter is the enclosing database environment
handle.
</p>
</li>
<li>
<p>
<code class="literal">offset_gbytes</code>
</p>
<p>
The <span class="bold"><strong>offset_gbytes</strong></span>
parameter specifies the number of gigabytes into
the output handle where the data can should be
written. This value, plus the value specified on
<code class="literal">offset_bytes</code>, indicates the
offset within the output handle where the backup
should begin.
</p>
</li>
<li>
<p>
<code class="literal">offset_bytes</code>
</p>
<p>
The <span class="bold"><strong>offset_bytes</strong></span>
parameter specifies the number of bytes into the
output handle where the data can be located. This
value, plus the value specified on
<code class="literal">offset_gbytes</code>, indicates the
offset within the output handle where the backup
should begin.
</p>
</li>
<li>
<p>
<code class="literal">size</code>
</p>
<p>
The <span class="bold"><strong>size</strong></span>
parameter specifies the number of bytes to back up
from the buffer.
</p>
</li>
<li>
<p>
<code class="literal">buf</code>
</p>
<p>
The <span class="bold"><strong>buf</strong></span>
parameter is the buffer which contains the data to
be backed up.
</p>
</li>
<li>
<p>
<code class="literal">handle</code>
</p>
<p>
The <span class="bold"><strong>handle</strong></span>
parameter references the handle (usually a file
handle) to which the backup will be written.
</p>
</li>
</ul>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp51803496"></a>close_func</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>close_func</strong></span> parameter
is the function used when ending a backup and closing a
backup target. The function takes three parameters:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<code class="literal">dbenv</code>
</p>
<p>
The <span class="bold"><strong>dbenv</strong></span>
parameter is the enclosing database environment
handle.
</p>
</li>
<li>
<p>
<code class="literal">dbname</code>
</p>
<p>
The <span class="bold"><strong>dbname</strong></span> parameter is the
name of the database that has now been backed up.
</p>
</li>
<li>
<p>
<code class="literal">handle</code>
</p>
<p>
The <span class="bold"><strong>handle</strong></span>
parameter references the handle (usually a file
handle) to which the backup was written, and which
now must be closed or otherwise discarded.
</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp51835480"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp51786112"></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_callbacks.html" title="DB_ENV->get_backup_callbacks()">DB_ENV->get_backup_callbacks()</a>,
<a class="xref" href="envbackup.html" title="DB_ENV->backup()">DB_ENV->backup()</a>, and
<a class="xref" href="envdbbackup.html" title="DB_ENV->dbbackup()">DB_ENV->dbbackup()</a>.
</p>
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