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Yasuhiro KIMURA
113 lines
5.4 KiB
HTML
113 lines
5.4 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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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="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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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 18. The Logging Subsystem" />
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<link rel="prev" href="log.html" title="Chapter 18. The Logging Subsystem" />
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<link rel="next" href="log_limits.html" title="Log file limits" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 18.1.40</p>
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</div>
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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 18. The Logging Subsystem </th>
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<td width="20%" align="right"> <a accesskey="n" href="log_limits.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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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>
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The aspects of logging that may be configured are the size
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of the logging subsystem's region, the size of the log files
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on disk, the size of the log buffer in memory, and several
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operating system settings affecting the behavior of log files.
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</p>
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<p>
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The <a href="../api_reference/C/envset_lg_regionmax.html" class="olink">DB_ENV->set_lg_regionmax()</a> method specifies the size of the logging
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subsystem's region, in bytes. The logging subsystem's default size
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is approximately 60KB. This value may need to be increased if a
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large number of files are registered with the Berkeley DB log
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manager, for example, by opening a large number of Berkeley DB
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database files in a transactional application.
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</p>
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<p>
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The <a href="../api_reference/C/envset_lg_max.html" class="olink">DB_ENV->set_lg_max()</a> method specifies the individual log file
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size for all the applications sharing the Berkeley DB
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environment. Setting the log file size is largely a matter of
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convenience and a reflection of the application's preferences
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in backup media and frequency. However, setting the log file
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size too low can potentially cause problems because it would
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be possible to run out of log sequence numbers, which requires
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a full archival and application restart to reset. See <a class="xref" href="log_limits.html" title="Log file limits">Log file limits</a> for more
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information.
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</p>
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<p>
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The <a href="../api_reference/C/envset_lg_bsize.html" class="olink">DB_ENV->set_lg_bsize()</a> method specifies the size of the
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in-memory log buffer, in bytes. Log information is stored in
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memory until the buffer fills up or transaction commit forces
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the buffer to be written to disk. Larger buffer sizes can
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significantly increase throughput in the presence of
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long-running transactions, highly concurrent applications, or
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transactions producing large amounts of data. By default, the
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buffer is approximately 32KB.
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</p>
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<p>
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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.
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</p>
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<p>
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The <a href="../api_reference/C/envset_lg_filemode.html" class="olink">DB_ENV->set_lg_filemode()</a> method specifies the absolute file
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mode for created log files. This method is only useful for the
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rare Berkeley DB application that does not control its umask
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value.
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</p>
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<p>
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The <a href="../api_reference/C/envlog_set_config.html" class="olink">DB_ENV->log_set_config()</a> method configures several boolean
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parameters that control the use of file system controls such
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as O_DIRECT and O_DSYNC, automatic removal of log files,
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in-memory logging, and pre-zeroing of logfiles.
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</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 18. The Logging Subsystem </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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