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<title>Berkeley DB: DbEnv::memp_sync</title>
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<h1>DbEnv::memp_sync</h1>
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#include <db_cxx.h>
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DbEnv::memp_sync(DbLsn *lsn);
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<p>The DbEnv::memp_sync method ensures that any modified pages in the pool with
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a log sequence number (<a href="../api_cxx/lsn_class.html">DbLsn</a>) less than the <b>lsn</b> argument
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are written to disk. The purpose of the <b>lsn</b> argument is to
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enable a transaction manager to ensure, as part of a checkpoint, that
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all pages modified by a certain time have been written to disk. Pages
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in the pool that cannot be immediately written back to disk (for
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example, pages that are currently in use by another thread of control)
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are waited for and written to disk as soon as it is possible to do so.
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If <b>lsn</b> is NULL, all modified pages in the pool are written
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<p>To support the DbEnv::memp_sync functionality, it is necessary that the
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pool functions know the location of the log sequence number on the page
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for each file type. This location should be specified when the file is
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opened using the <a href="../api_cxx/memp_set_lsn_offset.html">DbMpoolFile::set_lsn_offset</a> method. It is not required that
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the log sequence number be aligned on the page in any way.
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<p>The DbEnv::memp_sync method either returns a non-zero error value or throws an exception that
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encapsulates a non-zero error value on failure, and returns 0 on success.
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<p>The DbEnv::memp_sync method may fail and throw an exception or return a non-zero error for the following conditions:
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<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
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<p>The DbEnv::memp_sync function was called without logging having been
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initialized in the environment.
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<p>The DbEnv::memp_sync method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods.
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If a catastrophic error has occurred, the DbEnv::memp_sync method may fail and
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either return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a> or throw a
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<a href="../api_cxx/runrec_class.html">DbRunRecoveryException</a>,
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in which case all subsequent Berkeley DB calls will fail in the same way.
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<a href="../api_cxx/env_class.html">DbEnv</a>, <a href="../api_cxx/mempfile_class.html">DbMpoolFile</a>
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<a href="../api_cxx/memp_list.html">Memory Pools and Related Methods</a>
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