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<title>DB_ENV->set_lk_detect()</title>
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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_conflicts.html" title="DB_ENV->set_lk_conflicts()" />
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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->set_lk_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_conflicts.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="envset_lk_max_lockers.html">Next</a></td>
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</tr>
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</table>
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<hr />
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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="envset_lk_detect"></a>DB_ENV->set_lk_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->set_lk_detect(DB_ENV *dbenv, u_int32_t detect); </pre>
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<p>
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Set if the deadlock detector is to be run whenever a lock conflict
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occurs, and specify what lock request(s) should be rejected. As
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transactions acquire locks on behalf of a single locker ID, rejecting
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a lock request associated with a transaction normally requires the
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transaction be aborted.
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</p>
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<p>
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The database environment's deadlock detector configuration may also be
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configured using the environment's <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file. The
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syntax of the entry in that file is a single line with the string
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"set_lk_detect", one or more whitespace characters, and the method
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<span class="bold"><strong>detect</strong></span> parameter as a string; for
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example, "set_lk_detect DB_LOCK_OLDEST". Because the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a>
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file is read when the database environment is opened, it will
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silently overrule configuration done before that time.
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</p>
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<p>
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The <code class="methodname">DB_ENV->set_lk_detect()</code> method configures a database environment,
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not only operations performed using the specified <a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
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handle.
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</p>
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<p>
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The <code class="methodname">DB_ENV->set_lk_detect()</code> method may be
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called either before or after environment open, but once it is set
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it may not be changed again during the environment's lifetime.
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</p>
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<p>
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The <code class="methodname">DB_ENV->set_lk_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="idp60445912"></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="idp60455472"></a>detect</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>detect</strong></span> parameter configures the
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deadlock detector. The deadlock detector will reject the lock request
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with the lowest priority. If multiple lock requests have the lowest
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priority, then the <span class="bold"><strong>detect</strong></span> parameter
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is used to select which of those lock requests to reject. The
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specified value must be 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="set_lk_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 whatever lock policy was specified when the database environment
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was created. If no lock policy has yet been specified, set the lock
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policy to 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="set_lk_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="set_lk_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="set_lk_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="set_lk_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="set_lk_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="set_lk_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="set_lk_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="set_lk_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>
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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="idp60478688"></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->set_lk_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="idp60473040"></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="idp60470952"></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>,
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<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="idp60474120"></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_conflicts.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="envset_lk_max_lockers.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_conflicts() </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->set_lk_max_lockers()</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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