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<title>Berkeley DB: DB_ENV->set_lk_detect</title>
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<h1>DB_ENV->set_lk_detect</h1>
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DB_ENV->set_lk_detect(DB_ENV *dbenv, u_int32_t detect);
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<p>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. The specified value must be one of the
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<p><dt><a name="DB_LOCK_DEFAULT">DB_LOCK_DEFAULT</a><dd>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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<dt><a name="DB_LOCK_EXPIRE">DB_LOCK_EXPIRE</a><dd>Reject lock requests which have timed out. No other deadlock detection
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<dt><a name="DB_LOCK_MAXLOCKS">DB_LOCK_MAXLOCKS</a><dd>Reject the lock request for the locker ID with the greatest number of
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<dt><a name="DB_LOCK_MINLOCKS">DB_LOCK_MINLOCKS</a><dd>Reject the lock request for the locker ID with the fewest number of
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<dt><a name="DB_LOCK_MINWRITE">DB_LOCK_MINWRITE</a><dd>Reject the lock request for the locker ID with the fewest number of
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<dt><a name="DB_LOCK_OLDEST">DB_LOCK_OLDEST</a><dd>Reject the lock request for the oldest locker ID.
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<dt><a name="DB_LOCK_RANDOM">DB_LOCK_RANDOM</a><dd>Reject the lock request for a random locker ID.
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<dt><a name="DB_LOCK_YOUNGEST">DB_LOCK_YOUNGEST</a><dd>Reject the lock request for the youngest locker ID.
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<p>The DB_ENV->set_lk_detect method configures a database environment, not only operations
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performed using the specified <a href="../api_c/env_class.html">DB_ENV</a> handle.
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<p>The DB_ENV->set_lk_detect interface may not be called after the <a href="../api_c/env_open.html">DB_ENV->open</a>
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If the database environment already exists when
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<a href="../api_c/env_open.html">DB_ENV->open</a> is called, the information specified to DB_ENV->set_lk_detect
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must be consistent with the existing environment or an error will be
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<p>The DB_ENV->set_lk_detect method returns a non-zero error value on failure and 0 on success.
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<p>The database environment's deadlock detector configuration may also be set using the environment's
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<b>DB_CONFIG</b> file. The syntax of the entry in that file is a
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single line with the string "set_lk_detect", one or more whitespace characters,
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and the interface <b>detect</b> argument as a string; for example,
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"set_lk_detect DB_LOCK_OLDEST". Because the <b>DB_CONFIG</b> file is read when the database
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environment is opened, it will silently overrule configuration done
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<p>The DB_ENV->set_lk_detect method may fail and return a non-zero error for the following conditions:
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<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
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<p>Called after <a href="../api_c/env_open.html">DB_ENV->open</a> was called.
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<p>The DB_ENV->set_lk_detect method may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
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If a catastrophic error has occurred, the DB_ENV->set_lk_detect method may fail and
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return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>,
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in which case all subsequent Berkeley DB calls will fail in the same way.
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<a href="../api_c/env_class.html">DB_ENV</a>, <a href="../api_c/lock_class.html">DB_LOCK</a>
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<a href="../api_c/lock_list.html">Locking Subsystem and Related Methods</a>
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