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<!--$Id: lock_get.so,v 10.28 2000/04/24 16:33:54 bostic Exp $-->
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<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.-->
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<html>
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<head>
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<title>Berkeley DB: DbEnv::lock_get</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++">
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</head>
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<body bgcolor=white>
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<a name="2"><!--meow--></a>
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<table><tr valign=top>
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<td>
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<h1>DbEnv::lock_get</h1>
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</td>
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<td width="1%">
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<a href="../api_cxx/cxx_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<hr size=1 noshade>
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<tt>
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<h3><pre>
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#include <db_cxx.h>
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<p>
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int
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DbEnv::lock_get(u_int32_t locker, u_int32_t flags,
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const Dbt *obj, const db_lockmode_t lock_mode, DbLock *lock);
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</pre></h3>
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<h1>Description</h1>
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<p>The DbEnv::lock_get method acquires a lock from the lock table, returning
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information about it in
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the <b>lock</b> argument.
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<p>The <b>locker</b> argument specified to DbEnv::lock_get is an unsigned
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32-bit integer quantity. It represents the entity requesting or releasing
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the lock.
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<p>The <b>flags</b> value must be set to 0 or the following value:
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<p><dl compact>
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<p><dt><a name="DB_LOCK_NOWAIT">DB_LOCK_NOWAIT</a><dd>If a lock cannot be granted because the requested lock conflicts with an
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existing lock, return immediately instead of waiting for the lock to
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become available.
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</dl>
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<p>The <b>obj</b> argument is an untyped byte string that specifies the
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object to be locked or released.
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<p>The <b>mode</b> argument is an index into the environment's lock conflict
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array. See <a href="../api_cxx/env_set_lk_conflicts.html">DbEnv::set_lk_conflicts</a> and
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<a href="../ref/lock/stdmode.html">Standard Lock Modes</a>
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for a description of that array.
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<p>The DbEnv::lock_get method may
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return or throw an exception encapsulating
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one of the following values:
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<p><dl compact>
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<p><dt><a name="DB_LOCK_NOTGRANTED">DB_LOCK_NOTGRANTED</a><dd>A lock was requested that could not be immediately granted and the
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<b>flags</b> parameter was set to DB_LOCK_NOWAIT.
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</dl>
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<p>Otherwise, the DbEnv::lock_get method either returns a non-zero error value or throws an exception that
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encapsulates a non-zero error value on failure, and returns 0 on success.
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<h1>Errors</h1>
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<p>The DbEnv::lock_get method may fail and throw an exception or return a non-zero error for the following conditions:
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<p><dl compact>
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<p><dt>DB_LOCK_DEADLOCK<dd>The operation was selected to resolve a deadlock.
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</dl>
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<p><dl compact>
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<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
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</dl>
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<p><dl compact>
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<p><dt>ENOMEM<dd>The maximum number of locks has been reached.
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</dl>
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<p>The DbEnv::lock_get method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods.
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If a catastrophic error has occurred, the DbEnv::lock_get method may fail and either
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return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a> or throw an exception encapsulating
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<a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>, in which case all subsequent Berkeley DB calls will fail
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in the same way.
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<h3>Classes</h3>
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<a href="../api_cxx/dbenv_class.html">DbEnv</a>, <a href="../api_cxx/lock_class.html">DbLock</a>
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<h1>See Also</h1>
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<a href="../api_cxx/env_set_lk_conflicts.html">DbEnv::set_lk_conflicts</a>,
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<a href="../api_cxx/env_set_lk_detect.html">DbEnv::set_lk_detect</a>,
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<a href="../api_cxx/env_set_lk_max_locks.html">DbEnv::set_lk_max_locks</a>,
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<a href="../api_cxx/env_set_lk_max_lockers.html">DbEnv::set_lk_max_lockers</a>,
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<a href="../api_cxx/env_set_lk_max_objects.html">DbEnv::set_lk_max_objects</a>,
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<a href="../api_cxx/env_set_lk_max.html">DbEnv::set_lk_max</a>,
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<a href="../api_cxx/lock_detect.html">DbEnv::lock_detect</a>,
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<a href="../api_cxx/lock_get.html">DbEnv::lock_get</a>,
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<a href="../api_cxx/lock_id.html">DbEnv::lock_id</a>,
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<a href="../api_cxx/lock_put.html">DbLock::put</a>,
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<a href="../api_cxx/lock_stat.html">DbEnv::lock_stat</a>
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and
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<a href="../api_cxx/lock_vec.html">DbEnv::lock_vec</a>.
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</tt>
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<table><tr><td><br></td><td width="1%">
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<a href="../api_cxx/cxx_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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