mirror of
https://github.com/yasuhirokimura/db18
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Yasuhiro KIMURA
105 lines
5.1 KiB
HTML
105 lines
5.1 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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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>Database verification and salvage</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="am.html" title="Chapter 3. Access Method Operations" />
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<link rel="prev" href="am_upgrade.html" title="Database upgrade" />
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<link rel="next" href="am_sync.html" title="Flushing the database cache" />
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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">Database verification and
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salvage</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="am_upgrade.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 3. Access Method Operations </th>
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<td width="20%" align="right"> <a accesskey="n" href="am_sync.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="am_verify"></a>Database verification and
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salvage</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 <a href="../api_reference/C/dbverify.html" class="olink">DB->verify()</a> method verifies that a file, and any
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databases it may contain, are uncorrupted. In addition, the
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method may optionally be called with a file stream argument to
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which all key/data pairs found in the database are output.
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There are two modes for finding key/data pairs to be
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output:
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</p>
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<div class="orderedlist">
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<ol type="1">
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<li>
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If the <a href="../api_reference/C/dbverify.html#verify_DB_SALVAGE" class="olink">DB_SALVAGE</a> flag is specified, the key/data
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pairs in the database are output. When run in this mode,
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the database is assumed to be largely uncorrupted. For
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example, the <a href="../api_reference/C/dbverify.html" class="olink">DB->verify()</a> method will search for pages that
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are no longer linked into the database, and will output
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key/data pairs from such pages. However, key/data items
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that have been marked as deleted in the database will not
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be output, as the page structures are generally trusted in
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this mode.
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</li>
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<li>
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If both the <a href="../api_reference/C/dbverify.html#verify_DB_SALVAGE" class="olink">DB_SALVAGE</a> and <a href="../api_reference/C/dbverify.html#verify_DB_AGGRESSIVE" class="olink">DB_AGGRESSIVE</a> flags
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are specified, all possible key/data pairs are output.
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When run in this mode, the database is assumed to be
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seriously corrupted. For example, key/data pairs that have
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been deleted will re-appear in the output. In addition,
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because pages may have been subsequently reused and
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modified during normal database operations after the
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key/data pairs were deleted, it is not uncommon for
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apparently corrupted key/data pairs to be output in this
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mode, even when there is no corruption in the underlying
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database. The output will almost always have to be edited
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by hand or other means before the data is ready for reload
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into another database. We recommend that <a href="../api_reference/C/dbverify.html#verify_DB_SALVAGE" class="olink">DB_SALVAGE</a> be
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tried first, and <a href="../api_reference/C/dbverify.html#verify_DB_AGGRESSIVE" class="olink">DB_AGGRESSIVE</a> only tried if the output
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from that first attempt is obviously missing data items or
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the data is sufficiently valuable that human review of the
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output is preferable to any kind of data loss.
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</li>
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</ol>
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</div>
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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="am_upgrade.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="am.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="am_sync.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">Database upgrade </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"> Flushing the database cache</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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