<!--$Id: lock_vec.html,v 1.1 2003/02/15 04:55:53 zarzycki Exp $--> <!--Copyright 1997-2002 by Sleepycat Software, Inc.--> <!--All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB: DbEnv.lock_vec</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++"> </head> <body bgcolor=white> <a name="2"><!--meow--></a> <table width="100%"><tr valign=top> <td> <h1>DbEnv.lock_vec</h1> </td> <td align=right> <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> </td></tr></table> <hr size=1 noshade> <tt> <h3><pre> import com.sleepycat.db.*; <p> public void lock_vec(int locker, int flags, DbLockRequest[] list, int offset, int count) throws DbException </pre></h3> <h1>Description</h1> <p>The DbEnv.lock_vec method atomically obtains and releases one or more locks from the lock table. The DbEnv.lock_vec method is intended to support acquisition or trading of multiple locks under one lock table semaphore, as is needed for lock coupling or in multigranularity locking for lock escalation. <p>The <b>locker</b> argument specified to DbEnv.lock_vec is an unsigned 32-bit integer quantity. It represents the entity requesting or releasing the locks. <p>The <b>flags</b> value must be set to 0 or the following value: <p><dl compact> <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 an existing lock, throw a <a href="../api_java/lockng_class.html">DbLockNotGrantedException</a> immediately instead of waiting for the lock to become available. In this case, the index of the request that was not granted can be found by calling DbLockNotGrantedException.get_index. </dl> <p>The <b>list</b> array provided to DbEnv.lock_vec is a set of DbLockRequest objects. Only <b>count</b> elements of <b>list</b> starting at <b>offset</b> are considered by DbEnv.lock_vec. A DbLockRequest object has at least the following fields. For each field there is a corresponding get_ and set_ method <p><dl compact> <p><dt>int <a name="op">op</a>;<dd>The operation to be performed, which must be set to one of the following values: <p><dl compact> <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> structure fields, for the specified <b>locker</b>. Upon return from DbEnv.lock_vec, if the <b>lock</b> field is non-null, a reference to the acquired lock is stored there. (This reference is invalidated by any call to DbEnv.lock_vec or <a href="../api_java/lock_put.html">DbEnv.lock_put</a> that releases the lock.) <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> structure field overrides any previously specified timeout value for this lock. A value of 0 turns off any previously specified timeout. <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. The <b>locker</b> argument, and <b>mode</b> and <b>obj</b> fields are ignored. <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 <b>lock</b>, <b>mode</b>, and <b>obj</b> structure fields are ignored. Locks acquired in operations performed by the current call to DbEnv.lock_vec which appear before the Db.DB_LOCK_PUT_ALL operation are released; those acquired in operations appearing after the Db.DB_LOCK_PUT_ALL operation are not released. <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 <b>locker</b> argument and the <b>lock</b> and <b>mode</b> structure fields are ignored. Locks acquired in operations performed by the current call to DbEnv.lock_vec that appear before the Db.DB_LOCK_PUT_OBJ operation are released; those acquired in operations appearing after the Db.DB_LOCK_PUT_OBJ operation are not released. <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 database environment has not configured automatic deadlock detection, the transaction will timeout the next time deadlock detection is performed. As transactions acquire locks on behalf of a single locker ID, timing out the locker ID associated with a transaction will time out the transaction itself. </dl> <p><dt>DbLock <a name="lock">lock</a>;<dd>A lock reference. <p><dt>int <a name="mode">mode</a>;<dd>The lock mode, used as an index into the environment's lock conflict matrix. When using the default lock conflict matrix, <b>mode</b> must be set to one of the following values: <p><dl compact> <dt><a name="Db.DB_LOCK_READ">Db.DB_LOCK_READ</a><dd>read (shared) <dt><a name="Db.DB_LOCK_WRITE">Db.DB_LOCK_WRITE</a><dd>write (exclusive) <dt><a name="Db.DB_LOCK_IWRITE">Db.DB_LOCK_IWRITE</a><dd>intention to write (shared) <dt><a name="Db.DB_LOCK_IREAD">Db.DB_LOCK_IREAD</a><dd>intention to read (shared) <dt><a name="Db.DB_LOCK_IWR">Db.DB_LOCK_IWR</a><dd>intention to read and write (shared) </dl> <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. <p><dt>Dbt <a name="obj">obj</a>;<dd>An untyped byte string that specifies the object to be locked or released. Applications using the locking subsystem directly while also doing locking via the Berkeley DB access methods must take care not to inadvertently lock objects that happen to be equal to the unique file IDs used to lock files. See <a href="../ref/lock/am_conv.html">Access method locking conventions</a> for more information. <p><dt>int timeout;<dd>The lock timeout value. </dl> <p>If any of the requested locks cannot be acquired, or any of the locks to be released cannot be released, the operations before the failing operation are guaranteed to have completed successfully, and DbEnv.lock_vec throws an exception <p> Otherwise, the DbEnv.lock_vec method throws an exception that encapsulates a non-zero error value on failure. <h1>Errors</h1> <p>The DbEnv.lock_vec method may fail and throw an exception encapsulating a non-zero error for the following conditions: <p><dl compact> <p><dt>EINVAL<dd>An invalid flag value or parameter was specified. </dl> <p><dl compact> <p><dt>ENOMEM<dd>The maximum number of locks has been reached. </dl> <p>If the operation was selected to resolve a deadlock, the DbEnv.lock_vec method will fail and throw a <a href="../api_java/deadlock_class.html">DbDeadlockException</a> exception. <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. If a catastrophic error has occurred, the DbEnv.lock_vec method may fail and throw a <a href="../api_java/runrec_class.html">DbRunRecoveryException</a>, in which case all subsequent Berkeley DB calls will fail in the same way. <h1>Class</h1> <a href="../api_java/env_class.html">DbEnv</a>, <a href="../api_java/lock_class.html">DbLock</a> <h1>See Also</h1> <a href="../api_java/lock_list.html">Locking Subsystem and Related Methods</a> </tt> <table width="100%"><tr><td><br></td><td align=right> <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> </td></tr></table> <p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font> </body> </html>