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<!--$Id: memp_sync.so,v 10.41 2004/08/13 03:38:58 bostic Exp $-->
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<title>Berkeley DB: DbEnv::memp_sync</title>
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<h3>DbEnv::memp_sync</h3>
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<h3><pre>
#include <db_cxx.h>
<p>
int
DbEnv::memp_sync(DbLsn *lsn);
</pre></h3>
<hr size=1 noshade>
<h3>Description: DbEnv::memp_sync</h3>
<p>The DbEnv::memp_sync method flushes modified pages in the cache to their
backing files.</p>
<p>Pages in the pool that cannot be immediately written back to disk (for
example, pages that are currently in use by another thread of control)
are waited for and written to disk as soon as it is possible to do
so.</p>
<p>To support the DbEnv::memp_sync functionality, it is necessary that the
pool functions know the location of the log sequence number on the page
for each file type. This location should be specified when the file is
opened using the <a href="../api_cxx/memp_set_lsn_offset.html">DbMpoolFile::set_lsn_offset</a> method. It is not required that
the log sequence number be aligned on the page in any way.</p>
<p>The DbEnv::memp_sync 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.
</p>
<h3>Parameters</h3>
<dl compact>
<dt><b>lsn</b><dd>The purpose of the <b>lsn</b> parameter is to enable a transaction
manager to ensure, as part of a checkpoint, that all pages modified by
a certain time have been written to disk.
<p>All modified pages with a a log sequence number (<a href="../api_cxx/lsn_class.html">DbLsn</a>) less
than the <b>lsn</b> parameter are written to disk. If <b>lsn</b> is
NULL, all modified pages in the pool are written to disk.</p>
</dl>
<h3>Errors</h3>
<p>The DbEnv::memp_sync method
may fail and throw
<a href="../api_cxx/except_class.html">DbException</a>,
encapsulating one of the following non-zero errors, or return one of
the following non-zero errors:</p>
<dl compact>
<dt>EINVAL<dd>If the DbEnv::memp_sync function was called without logging having been
initialized in the environment; or if an
invalid flag value or parameter was specified.
</dl>
<hr size=1 noshade>
<h3>Class</h3>
<a href="../api_cxx/env_class.html">DbEnv</a>, <a href="../api_cxx/mempfile_class.html">DbMpoolFile</a>
<h3>See Also</h3>
<a href="../api_cxx/memp_list.html">Memory Pools and Related Methods</a>
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