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83 lines
4.1 KiB
HTML
<!--$Id: memp_sync.so,v 10.25 2000/09/08 15:20:28 bostic Exp $-->
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<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.-->
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<!--All rights reserved.-->
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<html>
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<head>
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<title>Berkeley DB: memp_sync</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++">
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</head>
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<body bgcolor=white>
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<a name="2"><!--meow--></a>
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<table><tr valign=top>
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<td>
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<h1>memp_sync</h1>
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</td>
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<td width="1%">
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<a href="../api_c/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<hr size=1 noshade>
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<tt>
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<h3><pre>
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#include <db.h>
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<p>
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int
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memp_sync(DB_ENV *env, DB_LSN *lsn);
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</pre></h3>
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<h1>Description</h1>
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<p>The memp_sync function ensures that any modified pages in the pool with
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log sequence numbers less than the <b>lsn</b> argument are written to
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disk. If <b>lsn</b> is NULL all modified pages in the pool are
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flushed.
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<p>The primary purpose of the memp_sync function is to enable a
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transaction manager to ensure, as part of a checkpoint, that all pages
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modified by a certain time have been written to disk. Pages in the pool
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that cannot be written back to disk immediately (e.g., that are currently
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pinned) are written to disk as soon as it is possible to do so. The
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expected behavior of the Berkeley DB or other transaction subsystem is to call
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the memp_sync function and then, if the return indicates that some
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pages could not be written immediately, to wait briefly and retry again
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with the same log sequence number until the memp_sync function
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returns that all pages have been written.
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<p>To support the 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_c/memp_fopen.html">memp_fopen</a> function. 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 memp_sync function returns a non-zero error value on failure, 0 on success, and returns <a href="../api_c/memp_fsync.html#DB_INCOMPLETE">DB_INCOMPLETE</a> if there were pages which need to be
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written but which memp_sync was unable to write immediately.
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In addition, if memp_sync returns success, the value of
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<b>lsn</b> will be overwritten with the largest log sequence number
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from any page which was written by memp_sync to satisfy this
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request.
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<h1>Errors</h1>
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<p>The memp_sync function may fail and return a non-zero error for the following conditions:
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<p><dl compact>
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<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
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<p>The memp_sync function was called without logging having been
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initialized in the environment.
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</dl>
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<p>The memp_sync function may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
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If a catastrophic error has occurred, the memp_sync function may fail and return
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<a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>, in which case all subsequent Berkeley DB calls will fail
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in the same way.
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<h1>See Also</h1>
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<a href="../api_c/env_set_mp_mmapsize.html">DBENV->set_mp_mmapsize</a>,
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<a href="../api_c/memp_fclose.html">memp_fclose</a>,
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<a href="../api_c/memp_fget.html">memp_fget</a>,
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<a href="../api_c/memp_fopen.html">memp_fopen</a>,
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<a href="../api_c/memp_fput.html">memp_fput</a>,
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<a href="../api_c/memp_fset.html">memp_fset</a>,
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<a href="../api_c/memp_fsync.html">memp_fsync</a>,
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<a href="../api_c/memp_register.html">memp_register</a>,
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<a href="../api_c/memp_stat.html">memp_stat</a>,
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<a href="../api_c/memp_sync.html">memp_sync</a>
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and
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<a href="../api_c/memp_trickle.html">memp_trickle</a>.
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</tt>
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<table><tr><td><br></td><td width="1%">
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<a href="../api_c/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font>
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</body>
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</html>
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