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<title>Berkeley DB: DbEnv.lock_vec</title>
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<h1>DbEnv.lock_vec</h1>
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<a href="../api_java/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../reftoc.html"><img src="../images/ref.gif" alt="Ref"></a>
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import com.sleepycat.db.*;
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public void lock_vec(int locker, int flags, DbLockRequest[] list,
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int offset, int count)
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<p>The DbEnv.lock_vec method atomically obtains and releases one or more locks
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from the lock table. The DbEnv.lock_vec method is intended to support
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acquisition or trading of multiple locks under one lock table semaphore,
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as is needed for lock coupling or in multigranularity locking for lock
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<p>The <b>locker</b> argument specified to DbEnv.lock_vec is an unsigned
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32-bit integer quantity. It represents the entity requesting or releasing
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<p>The <b>flags</b> value must be set to 0 or
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<p><dt><a name="Db.DB_LOCK_NOWAIT">Db.DB_LOCK_NOWAIT</a><dd>If a lock cannot be granted because the requested lock conflicts with
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throw a <a href="../api_java/lockng_class.html">DbLockNotGrantedException</a> immediately instead of waiting
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for the lock to become available. In this case, the index of the request
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that was not granted can be found by calling
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DbLockNotGrantedException.get_index.
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<p>The <b>list</b> array provided to DbEnv.lock_vec is a set of
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DbLockRequest objects. Only <b>count</b> elements of <b>list</b>
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starting at <b>offset</b> are considered by DbEnv.lock_vec.
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A DbLockRequest object has at least the following fields.
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For each field there is a corresponding get_ and set_ method
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<p><dt>int <a name="op">op</a>;<dd>The operation to be performed, which must be set to one of the
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<p><dt><a name="Db.DB_LOCK_GET">Db.DB_LOCK_GET</a><dd>Get the lock defined by the values of the <b>mode</b> and <b>obj</b>
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structure fields, for the specified <b>locker</b>. Upon return from
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DbEnv.lock_vec, if the <b>lock</b> field is non-null, a reference
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to the acquired lock is stored there. (This reference is invalidated
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by any call to DbEnv.lock_vec or <a href="../api_java/lock_put.html">DbEnv.lock_put</a> that releases the
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<p><dt><a name="Db.DB_LOCK_GET_TIMEOUT">Db.DB_LOCK_GET_TIMEOUT</a><dd>Identical to Db.DB_LOCK_GET except that the value in the <b>timeout</b>
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structure field overrides any previously specified timeout value for
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this lock. A value of 0 turns off any previously specified timeout.
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<p><dt><a name="Db.DB_LOCK_PUT">Db.DB_LOCK_PUT</a><dd>The lock to which the <b>lock</b> structure field refers is released.
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The <b>locker</b> argument, and <b>mode</b> and <b>obj</b> fields
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<p><dt><a name="Db.DB_LOCK_PUT_ALL">Db.DB_LOCK_PUT_ALL</a><dd>All locks held by the specified <b>locker</b> are released. The
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<b>lock</b>, <b>mode</b>, and <b>obj</b> structure fields are
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ignored. Locks acquired in operations performed by the current call to
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DbEnv.lock_vec which appear before the Db.DB_LOCK_PUT_ALL
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operation are released; those acquired in operations appearing after
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the Db.DB_LOCK_PUT_ALL operation are not released.
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<p><dt><a name="Db.DB_LOCK_PUT_OBJ">Db.DB_LOCK_PUT_OBJ</a><dd>All locks held on the object <b>obj</b> are released. The
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<b>locker</b> argument and the <b>lock</b> and <b>mode</b> structure
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fields are ignored. Locks acquired in operations performed by the
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current call to DbEnv.lock_vec that appear before the
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Db.DB_LOCK_PUT_OBJ operation are released; those acquired in
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operations appearing after the Db.DB_LOCK_PUT_OBJ operation are
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<p><dt><a name="Db.DB_LOCK_TIMEOUT">Db.DB_LOCK_TIMEOUT</a><dd>Cause the specified <b>locker</b> to timeout immediately. If the
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database environment has not configured automatic deadlock detection,
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the transaction will timeout the next time deadlock detection is
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performed. As transactions acquire locks on behalf of a single locker
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ID, timing out the locker ID associated with a transaction will time
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out the transaction itself.
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<p><dt>DbLock <a name="lock">lock</a>;<dd>A lock reference.
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<p><dt>int <a name="mode">mode</a>;<dd>The lock mode, used as an index into the environment's lock conflict matrix.
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When using the default lock conflict matrix, <b>mode</b> must be set to one
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of the following values:
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<dt><a name="Db.DB_LOCK_READ">Db.DB_LOCK_READ</a><dd>read (shared)
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<dt><a name="Db.DB_LOCK_WRITE">Db.DB_LOCK_WRITE</a><dd>write (exclusive)
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<dt><a name="Db.DB_LOCK_IWRITE">Db.DB_LOCK_IWRITE</a><dd>intention to write (shared)
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<dt><a name="Db.DB_LOCK_IREAD">Db.DB_LOCK_IREAD</a><dd>intention to read (shared)
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<dt><a name="Db.DB_LOCK_IWR">Db.DB_LOCK_IWR</a><dd>intention to read and write (shared)
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<p>See <a href="../api_java/env_set_lk_conflicts.html">DbEnv.set_lk_conflicts</a> and <a href="../ref/lock/stdmode.html">Standard Lock Modes</a> for more information on the lock conflict matrix.
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<p><dt>Dbt <a name="obj">obj</a>;<dd>An untyped byte string that specifies the object to be locked or
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released. Applications using the locking subsystem directly while also
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doing locking via the Berkeley DB access methods must take care not to
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inadvertently lock objects that happen to be equal to the unique file
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IDs used to lock files. See <a href="../ref/lock/am_conv.html">Access
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method locking conventions</a> for more information.
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<p><dt>int timeout;<dd>The lock timeout value.
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<p>If any of the requested locks cannot be acquired, or any of the locks to
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be released cannot be released, the operations before the failing
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operation are guaranteed to have completed successfully, and
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DbEnv.lock_vec throws an exception
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Otherwise, the DbEnv.lock_vec method throws an exception that encapsulates a non-zero error value on
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<p>The DbEnv.lock_vec method may fail and throw an exception encapsulating 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><dt>ENOMEM<dd>The maximum number of locks has been reached.
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<p>If the operation was selected to resolve a deadlock, the
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DbEnv.lock_vec method will fail and
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throw a <a href="../api_java/deadlock_class.html">DbDeadlockException</a> exception.
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<p>The DbEnv.lock_vec method may fail and throw an exception 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_vec method may fail and
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throw a <a href="../api_java/runrec_class.html">DbRunRecoveryException</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_java/env_class.html">DbEnv</a>, <a href="../api_java/lock_class.html">DbLock</a>
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<a href="../api_java/lock_list.html">Locking Subsystem and Related Methods</a>
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