1<!--$Id: env_set_lk_detect.so,v 10.50 2006/02/27 14:51:30 bostic Exp $--> 2<!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> 3<!--See the file LICENSE for redistribution information.--> 4<html> 5<head> 6<title>Berkeley DB: DbEnv::set_lk_detect</title> 7<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> 8<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> 9</head> 10<body bgcolor=white> 11<table width="100%"><tr valign=top> 12<td> 13<b>DbEnv::set_lk_detect</b> 14</td> 15<td align=right> 16<a href="/api_cxx/api_core.html"><img src="/images/api.gif" alt="API"></a> 17<a href="/ref/toc.html"><img src="/images/ref.gif" alt="Ref"></a></td> 18</tr></table> 19<hr size=1 noshade> 20<tt> 21<b><pre> 22#include <db_cxx.h> 23<p> 24int 25DbEnv::set_lk_detect(u_int32_t detect); 26<p> 27int 28DbEnv::get_lk_detect(u_int32_t *lk_detectp); 29</pre></b> 30<hr size=1 noshade> 31<b>Description: DbEnv::set_lk_detect</b> 32<p>Set if the deadlock detector is to be run whenever a lock conflict 33occurs, and specify what lock request(s) should be rejected. As 34transactions acquire locks on behalf of a single locker ID, rejecting a 35lock request associated with a transaction normally requires the 36transaction be aborted.</p> 37<p>The database environment's deadlock detector configuration may also be configured using the 38environment's <a href="/ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file. The syntax of the entry in that 39file is a single line with the string "set_lk_detect", one or more whitespace 40characters, and the method <b>detect</b> parameter as a string; for example, 41"set_lk_detect DB_LOCK_OLDEST". 42Because the <a href="/ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file is read when the database environment 43is opened, it will silently overrule configuration done before that 44time.</p> 45<p>The DbEnv::set_lk_detect method configures a database environment, not only operations 46performed using the specified <a href="/api_cxx/env_class.html">DbEnv</a> handle.</p> 47<p>The DbEnv::set_lk_detect method may be called at any time during the life of the 48application.</p> 49<p>The DbEnv::set_lk_detect method 50either returns a non-zero error value 51or throws an exception that encapsulates a non-zero error value on 52failure, and returns 0 on success. 53</p> 54<b>Parameters</b> <br> 55 <b>detect</b><ul compact><li>The <b>detect</b> parameter configures the deadlock detector. The 56specified value must be one of the following list: 57<br> 58<b><a name="DB_LOCK_DEFAULT">DB_LOCK_DEFAULT</a></b><ul compact><li>Use whatever lock policy was specified when the database environment 59was created. If no lock policy has yet been specified, set the lock 60policy to DB_LOCK_RANDOM.</ul> 61<b><a name="DB_LOCK_EXPIRE">DB_LOCK_EXPIRE</a></b><ul compact><li>Reject lock requests which have timed out. No other deadlock detection 62is performed.</ul> 63<b><a name="DB_LOCK_MAXLOCKS">DB_LOCK_MAXLOCKS</a></b><ul compact><li>Reject the lock request for the locker ID with the most locks.</ul> 64<b><a name="DB_LOCK_MAXWRITE">DB_LOCK_MAXWRITE</a></b><ul compact><li>Reject the lock request for the locker ID with the most write locks.</ul> 65<b><a name="DB_LOCK_MINLOCKS">DB_LOCK_MINLOCKS</a></b><ul compact><li>Reject the lock request for the locker ID with the fewest locks.</ul> 66<b><a name="DB_LOCK_MINWRITE">DB_LOCK_MINWRITE</a></b><ul compact><li>Reject the lock request for the locker ID with the fewest write locks.</ul> 67<b><a name="DB_LOCK_OLDEST">DB_LOCK_OLDEST</a></b><ul compact><li>Reject the lock request for the locker ID with the oldest lock.</ul> 68<b><a name="DB_LOCK_RANDOM">DB_LOCK_RANDOM</a></b><ul compact><li>Reject the lock request for a random locker ID.</ul> 69<b><a name="DB_LOCK_YOUNGEST">DB_LOCK_YOUNGEST</a></b><ul compact><li>Reject the lock request for the locker ID with the youngest lock.</ul> 70<br></ul> 71<br> 72<br><b>Errors</b> 73<p>The DbEnv::set_lk_detect method 74may fail and throw 75<a href="/api_cxx/except_class.html">DbException</a>, 76encapsulating one of the following non-zero errors, or return one of 77the following non-zero errors:</p> 78<br> 79<b>EINVAL</b><ul compact><li>An 80invalid flag value or parameter was specified.</ul> 81<br> 82<hr size=1 noshade> 83<b>Description: DbEnv::get_lk_detect</b> 84<p>The DbEnv::get_lk_detect method returns the deadlock detector configuration.</p> 85<p>The DbEnv::get_lk_detect method may be called at any time during the life of the 86application.</p> 87<p>The DbEnv::get_lk_detect method 88either returns a non-zero error value 89or throws an exception that encapsulates a non-zero error value on 90failure, and returns 0 on success. 91</p> 92<b>Parameters</b> <br> 93 <b>lk_detectp</b><ul compact><li>The DbEnv::get_lk_detect method returns the 94deadlock detector configuration in <b>lk_detectp</b>.</ul> 95<br> 96<hr size=1 noshade> 97<br><b>Class</b> 98<a href="/api_cxx/env_class.html">DbEnv</a>, <a href="/api_cxx/lock_class.html">DbLock</a> 99<br><b>See Also</b> 100<a href="/api_cxx/lock_list.html">Locking Subsystem and Related Methods</a> 101</tt> 102<table width="100%"><tr><td><br></td><td align=right> 103<a href="/api_cxx/api_core.html"><img src="/images/api.gif" alt="API"></a><a href="/ref/toc.html"><img src="/images/ref.gif" alt="Ref"></a> 104</td></tr></table> 105<p><font size=1>Copyright (c) 1996,2008 Oracle. 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