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97 lines
5.1 KiB
HTML
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>Configuring logging</title>
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<link rel="start" href="index.html" title="Berkeley DB Programmer's Reference Guide" />
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<link rel="up" href="log.html" title="Chapter 17. The Logging Subsystem" />
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<p>Library Version 11.2.5.3</p>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Configuring logging</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="log.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 17.
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The Logging Subsystem
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="log_limits.html">Next</a></td>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="log_config"></a>Configuring logging</h2>
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</div>
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</div>
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</div>
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<p>The aspects of logging that may be configured are the size of the
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logging subsystem's region, the size of the log files on disk and the
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size of the log buffer in memory. The <a href="../api_reference/C/envset_lg_regionmax.html" class="olink">DB_ENV->set_lg_regionmax()</a> method
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specifies the size of the logging subsystem's region, in bytes. The
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logging subsystem's default size is approximately 60KB. This value may
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need to be increased if a large number of files are registered with the
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Berkeley DB log manager, for example, by opening a large number of Berkeley DB
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database files in a transactional application.</p>
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<p>The <a href="../api_reference/C/envset_lg_max.html" class="olink">DB_ENV->set_lg_max()</a> method specifies the individual log file size for
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all the applications sharing the Berkeley DB environment. Setting the log
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file size is largely a matter of convenience and a reflection of the
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application's preferences in backup media and frequency. However,
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setting the log file size too low can potentially cause problems because
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it would be possible to run out of log sequence numbers, which requires
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a full archival and application restart to reset. See
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<a class="xref" href="log_limits.html" title="Log file limits">Log file limits</a> for more
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information.</p>
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<p>The <a href="../api_reference/C/envset_lg_bsize.html" class="olink">DB_ENV->set_lg_bsize()</a> method specifies the size of the in-memory log
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buffer, in bytes. Log information is stored in memory until the buffer
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fills up or transaction commit forces the buffer to be written to disk.
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Larger buffer sizes can significantly increase throughput in the
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presence of long-running transactions, highly concurrent applications,
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or transactions producing large amounts of data. By default, the buffer
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is approximately 32KB.</p>
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<p>The <a href="../api_reference/C/envset_lg_dir.html" class="olink">DB_ENV->set_lg_dir()</a> method specifies the directory in which
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log files will be placed. By default, log files are placed in
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the environment home directory.</p>
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<p>The <a href="../api_reference/C/envset_lg_filemode.html" class="olink">DB_ENV->set_lg_filemode()</a> method specifies the absolute file mode for
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created log files. This method is only useful for the rare Berkeley DB
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application that does not control its umask value.</p>
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<p>The <a href="../api_reference/C/envlog_set_config.html" class="olink">DB_ENV->log_set_config()</a> method configures several boolean parameters
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that control the use of file system controls such as O_DIRECT and O_DSYNC,
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automatic removal of log files, in-memory logging, and pre-zeroing of logfiles.</p>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="log.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="log.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="log_limits.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Chapter 17.
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The Logging Subsystem
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</td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> Log file limits</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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