mirror of
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93 lines
4.8 KiB
HTML
93 lines
4.8 KiB
HTML
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<?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 11.2.5.2</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 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.
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Access Method Operations
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</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 salvage</h2>
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</div>
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</div>
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</div>
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<p>The <a href="../api_reference/C/dbverify.html" class="olink">DB->verify()</a> method verifies that a file, and any databases it may
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contain, are uncorrupted. In addition, the method may optionally be
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called with a file stream argument to which all key/data pairs found in
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the database are output. There are two modes for finding key/data pairs
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to be output:</p>
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<div class="orderedlist">
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<ol type="1">
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<li>If the <a href="../api_reference/C/dbverify.html#verify_DB_SALVAGE" class="olink">DB_SALVAGE</a> flag is specified, the key/data pairs in the
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database are output. When run in this mode, the database is assumed to
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be largely uncorrupted. For example, the <a href="../api_reference/C/dbverify.html" class="olink">DB->verify()</a> method will
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search for pages that are no longer linked into the database, and will
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output key/data pairs from such pages. However, key/data items that
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have been marked as deleted in the database will not be output, as the
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page structures are generally trusted in this mode.</li>
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<li>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 are
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specified, all possible key/data pairs are output. When run in this mode,
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the database is assumed to be seriously corrupted. For example, key/data
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pairs that have been deleted will re-appear in the output. In addition,
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because pages may have been subsequently reused and modified during
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normal database operations after the key/data pairs were deleted, it is
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not uncommon for apparently corrupted key/data pairs to be output in this
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mode, even when there is no corruption in the underlying database. The
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output will almost always have to be edited by hand or other means before
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the data is ready for reload into another database. We recommend that
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<a href="../api_reference/C/dbverify.html#verify_DB_SALVAGE" class="olink">DB_SALVAGE</a> be tried first, and <a href="../api_reference/C/dbverify.html#verify_DB_AGGRESSIVE" class="olink">DB_AGGRESSIVE</a> only tried
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if the output from that first attempt is obviously missing data items or
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the data is sufficiently valuable that human review of the output is
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preferable to any kind of data loss.</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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