<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>DbEnv::set_lk_detect()</title> <link rel="stylesheet" href="apiReference.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> <link rel="start" href="index.html" title="Berkeley DB C++ API Reference" /> <link rel="up" href="lock.html" title="Chapter 7. The DbLock Handle" /> <link rel="prev" href="envset_lk_conflicts.html" title="DbEnv::set_lk_conflicts()" /> <link rel="next" href="envset_lk_max_lockers.html" title="DbEnv::set_lk_max_lockers()" /> </head> <body> <div xmlns="" class="navheader"> <div class="libver"> <p>Library Version 11.2.5.3</p> </div> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">DbEnv::set_lk_detect()</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="envset_lk_conflicts.html">Prev</a> </td> <th width="60%" align="center">Chapter 7. The DbLock Handle </th> <td width="20%" align="right"> <a accesskey="n" href="envset_lk_max_lockers.html">Next</a></td> </tr> </table> <hr /> </div> <div class="sect1" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h2 class="title" style="clear: both"><a id="envset_lk_detect"></a>DbEnv::set_lk_detect()</h2> </div> </div> </div> <pre class="programlisting">#include <db_cxx.h> int DbEnv::set_lk_detect(u_int32_t detect); </pre> <p> Set if the deadlock detector is to be run whenever a lock conflict occurs, and specify what lock request(s) should be rejected. As transactions acquire locks on behalf of a single locker ID, rejecting a lock request associated with a transaction normally requires the transaction be aborted. </p> <p> The database environment's deadlock detector configuration may also be 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 syntax of the entry in that file is a single line with the string "set_lk_detect", one or more whitespace characters, and the method <span class="bold"><strong>detect</strong></span> parameter as a string; for 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> file is read when the database environment is opened, it will silently overrule configuration done before that time. </p> <p> The <code class="methodname">DbEnv::set_lk_detect()</code> method configures a database environment, not only operations performed using the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle. </p> <p> The <code class="methodname">DbEnv::set_lk_detect()</code> method may be called either before or after environment open, but once it is set it may not be changed again during the environment's lifetime. </p> <p> The <code class="methodname">DbEnv::set_lk_detect()</code> <span> <span> method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success. </span> </span> </p> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp2560448"></a>Parameters</h3> </div> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp2560184"></a>detect</h4> </div> </div> </div> <p> The <span class="bold"><strong>detect</strong></span> parameter configures the deadlock detector. The deadlock detector will reject the lock request with the lowest priority. If multiple lock requests have the lowest priority, then the <span class="bold"><strong>detect</strong></span> parameter is used to select which of those lock requests to reject. The specified value must be one of the following list: </p> <div class="itemizedlist"> <ul type="disc"> <li> <p><a id="set_lk_detect_DB_LOCK_DEFAULT"></a> <code class="literal">DB_LOCK_DEFAULT</code> </p> <p> Use whatever lock policy was specified when the database environment was created. If no lock policy has yet been specified, set the lock policy to DB_LOCK_RANDOM. </p> </li> <li> <p><a id="set_lk_detect_DB_LOCK_EXPIRE"></a> <code class="literal">DB_LOCK_EXPIRE</code> </p> <p> Reject lock requests which have timed out. No other deadlock detection is performed. </p> </li> <li> <p><a id="set_lk_detect_DB_LOCK_MAXLOCKS"></a> <code class="literal">DB_LOCK_MAXLOCKS</code> </p> <p> Reject the lock request for the locker ID with the most locks. </p> </li> <li> <p><a id="set_lk_detect_DB_LOCK_MAXWRITE"></a> <code class="literal">DB_LOCK_MAXWRITE</code> </p> <p> Reject the lock request for the locker ID with the most write locks. </p> </li> <li> <p><a id="set_lk_detect_DB_LOCK_MINLOCKS"></a> <code class="literal">DB_LOCK_MINLOCKS</code> </p> <p> Reject the lock request for the locker ID with the fewest locks. </p> </li> <li> <p><a id="set_lk_detect_DB_LOCK_MINWRITE"></a> <code class="literal">DB_LOCK_MINWRITE</code> </p> <p> Reject the lock request for the locker ID with the fewest write locks. </p> </li> <li> <p><a id="set_lk_detect_DB_LOCK_OLDEST"></a> <code class="literal">DB_LOCK_OLDEST</code> </p> <p> Reject the lock request for the locker ID with the oldest lock. </p> </li> <li> <p><a id="set_lk_detect_DB_LOCK_RANDOM"></a> <code class="literal">DB_LOCK_RANDOM</code> </p> <p> Reject the lock request for a random locker ID. </p> </li> <li> <p><a id="set_lk_detect_DB_LOCK_YOUNGEST"></a> <code class="literal">DB_LOCK_YOUNGEST</code> </p> <p> Reject the lock request for the locker ID with the youngest lock. </p> </li> </ul> </div> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp2578368"></a>Errors</h3> </div> </div> </div> <p> The <code class="methodname">DbEnv::set_lk_detect()</code> <span> <span> method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a> exception, encapsulating one of the following non-zero errors, or return one of the following non-zero errors: </span> </span> </p> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp2575344"></a>EINVAL</h4> </div> </div> </div> <p> An invalid flag value or parameter was specified. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp2550456"></a>Class</h3> </div> </div> </div> <p> <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>, <a class="link" href="lock.html" title="Chapter 7. The DbLock Handle">DbLock</a> </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp2576376"></a>See Also</h3> </div> </div> </div> <p> <a class="xref" href="lock.html#locklist" title="Locking Subsystem and Related Methods">Locking Subsystem and Related Methods</a> </p> </div> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="envset_lk_conflicts.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="lock.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="envset_lk_max_lockers.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">DbEnv::set_lk_conflicts() </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> DbEnv::set_lk_max_lockers()</td> </tr> </table> </div> </body> </html>