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271 lines
10 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>DB_ENV->lock_detect()</title>
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<link rel="stylesheet" href="apiReference.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 C API Reference" />
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<link rel="up" href="lock.html" title="Chapter 6. The DB_LOCK Handle" />
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<link rel="prev" href="envset_lk_tablesize.html" title="DB_ENV->set_lk_tablesize()" />
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<link rel="next" href="lockget.html" title="DB_ENV->lock_get()" />
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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 11.2.5.3</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">DB_ENV->lock_detect()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="envset_lk_tablesize.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 6.
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The DB_LOCK Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="lockget.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="lockdetect"></a>DB_ENV->lock_detect()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db.h>
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int
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DB_ENV->lock_detect(DB_ENV *env,
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u_int32_t flags, u_int32_t atype, int *rejected); </pre>
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<p>
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The <code class="methodname">DB_ENV->lock_detect()</code> method runs one iteration of the deadlock
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detector. The deadlock detector traverses the lock table and marks one
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of the participating lock requesters for rejection in each deadlock it
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finds.
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</p>
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<p>
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The <code class="methodname">DB_ENV->lock_detect()</code> method is the underlying method used by the
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<a class="link" href="db_deadlock.html" title="db_deadlock">db_deadlock</a> utility.
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See the <a class="link" href="db_deadlock.html" title="db_deadlock">db_deadlock</a>
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utility source code for an example of using <code class="methodname">DB_ENV->lock_detect()</code> in
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a IEEE/ANSI Std 1003.1 (POSIX) environment.
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</p>
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<p>
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The <code class="methodname">DB_ENV->lock_detect()</code> <span>
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<span>
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method returns a non-zero error value on failure and 0 on success.
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</span>
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</span>
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</p>
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<div class="sect2" 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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<h3 class="title"><a id="idp60554360"></a>Parameters</h3>
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</div>
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</div>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="idp60565384"></a>flags</h4>
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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 <span class="bold"><strong>flags</strong></span> parameter is currently
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unused, and must be set to 0.
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</p>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="idp60567832"></a>atype</h4>
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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 <span class="bold"><strong>atype</strong></span> parameter specifies which
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lock request(s) to reject. The deadlock detector will reject the lock
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request with the lowest priority. If multiple lock requests have the
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lowest priority, then the <span class="bold"><strong>atype</strong></span>
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parameter is used to select which of those lock requests to reject.
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It must be set to one of the following list:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p><a id="detect_DB_LOCK_DEFAULT"></a>
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<code class="literal">DB_LOCK_DEFAULT</code>
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</p>
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<p>
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Use the default lock policy, which is DB_LOCK_RANDOM.
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</p>
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</li>
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<li>
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<p><a id="detect_DB_LOCK_EXPIRE"></a>
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<code class="literal">DB_LOCK_EXPIRE</code>
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</p>
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<p>
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Reject lock requests which have timed out. No other deadlock
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detection is performed.
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</p>
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</li>
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<li>
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<p><a id="detect_DB_LOCK_MAXLOCKS"></a>
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<code class="literal">DB_LOCK_MAXLOCKS</code>
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</p>
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<p>
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Reject the lock request for the locker ID with the most locks.
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</p>
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</li>
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<li>
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<p><a id="detect_DB_LOCK_MAXWRITE"></a>
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<code class="literal">DB_LOCK_MAXWRITE</code>
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</p>
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<p>
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Reject the lock request for the locker ID with the most write locks.
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</p>
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</li>
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<li>
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<p><a id="detect_DB_LOCK_MINLOCKS"></a>
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<code class="literal">DB_LOCK_MINLOCKS</code>
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</p>
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<p>
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Reject the lock request for the locker ID with the fewest locks.
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</p>
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</li>
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<li>
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<p><a id="detect_DB_LOCK_MINWRITE"></a>
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<code class="literal">DB_LOCK_MINWRITE</code>
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</p>
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<p>
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Reject the lock request for the locker ID with the fewest write locks.
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</p>
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</li>
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<li>
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<p><a id="detect_DB_LOCK_OLDEST"></a>
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<code class="literal">DB_LOCK_OLDEST</code>
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</p>
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<p>
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Reject the lock request for the locker ID with the oldest lock.
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</p>
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</li>
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<li>
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<p><a id="detect_DB_LOCK_RANDOM"></a>
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<code class="literal">DB_LOCK_RANDOM</code>
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</p>
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<p>
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Reject the lock request for a random locker ID.
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</p>
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</li>
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<li>
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<p><a id="detect_DB_LOCK_YOUNGEST"></a>
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<code class="literal">DB_LOCK_YOUNGEST</code>
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</p>
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<p>
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Reject the lock request for the locker ID with the youngest lock.
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</p>
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</li>
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</ul>
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</div>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="idp60583992"></a>rejected</h4>
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</div>
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</div>
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</div>
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<p>
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If the <span class="bold"><strong>rejected</strong></span> parameter is
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non-NULL, the memory location to which it refers will be set to the
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number of lock requests that were rejected.
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</p>
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</div>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="idp60568272"></a>Errors</h3>
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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 <code class="methodname">DB_ENV->lock_detect()</code> <span>
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<span>
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method may fail and return one of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" 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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<h4 class="title"><a id="idp60578560"></a>EINVAL</h4>
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</div>
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</div>
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</div>
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<p>
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An invalid flag value or parameter was specified.
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</p>
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</div>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="idp60585072"></a>Class</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>, <a class="link" href="lock.html" title="Chapter 6. The DB_LOCK Handle">DB_LOCK</a>
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</p>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="idp60587120"></a>See Also</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="xref" href="lock.html#locklist" title="Locking Subsystem and Related Methods">Locking Subsystem and Related Methods</a>
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</p>
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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="envset_lk_tablesize.html">Prev</a> </td>
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||
<td width="20%" align="center">
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<a accesskey="u" href="lock.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="lockget.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">DB_ENV->set_lk_tablesize() </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"> DB_ENV->lock_get()</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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