<!--$Id: lock_vec.so,v 10.70 2007/10/26 15:01:06 bostic Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB: DB_ENV->lock_vec</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> </head> <body bgcolor=white> <table width="100%"><tr valign=top> <td> <b>DB_ENV->lock_vec</b> </td> <td align=right> <a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a> <a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td> </tr></table> <hr size=1 noshade> <tt> <b><pre> #include <db.h> <p> int DB_ENV->lock_vec(DB_ENV *env, u_int32_t locker, u_int32_t flags, DB_LOCKREQ list[], int nlist, DB_LOCKREQ **elistp); </pre></b> <hr size=1 noshade> <b>Description: DB_ENV->lock_vec</b> <p>The DB_ENV->lock_vec method atomically obtains and releases one or more locks from the lock table. The DB_ENV->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> <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 DB_ENV->lock_vec returns a non-zero value. In addition, if <b>elistp</b> is not NULL, it is set to point to the DB_LOCKREQ entry that was being processed when the error occurred.</p> <p>Unless otherwise specified, the DB_ENV->lock_vec method returns a non-zero error value on failure and 0 on success. </p> <b>Parameters</b> <br> <b>elistp</b><ul compact><li>If an error occurs, and the <b>elistp</b> parameter is non-NULL, it is set to point to the DB_LOCKREQ entry that was being processed when the error occurred.</ul> <b>flags</b><ul compact><li>The <b>flags</b> parameter must be set to 0 or the following value: <br> <b><a name="DB_LOCK_NOWAIT">DB_LOCK_NOWAIT</a></b><ul compact><li>If a lock cannot be granted because the requested lock conflicts with an existing lock, return DB_LOCK_NOTGRANTED immediately instead of waiting for the lock to become available. In this case, if non-NULL, <b>elistp</b> identifies the request that was not granted. </ul> <br></ul> <b>locker</b><ul compact><li>The <b>locker</b> parameter is an unsigned 32-bit integer quantity. It represents the entity requesting or releasing the lock.</ul> <b>list</b><ul compact><li>The <b>list</b> array provided to DB_ENV->lock_vec is typedef'd as DB_LOCKREQ. <p>To ensure compatibility with future releases of Berkeley DB, all fields of the DB_LOCKREQ structure that are not explicitly set should be initialized to 0 before the first time the structure is used. Do this by declaring the structure external or static, or by calling <b>memset</b>(3).</p> <p>A DB_LOCKREQ structure has at least the following fields:</p> <br> <b>lockop_t <a name="op">op</a>;</b><ul compact><li>The operation to be performed, which must be set to one of the following values:</ul> <br> <b><a name="DB_LOCK_GET">DB_LOCK_GET</a></b><ul compact><li>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 DB_ENV->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 DB_ENV->lock_vec or <a href="../api_c/lock_put.html">DB_ENV->lock_put</a> that releases the lock.)</ul> <b><a name="DB_LOCK_GET_TIMEOUT">DB_LOCK_GET_TIMEOUT</a></b><ul compact><li>Identical to 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.</ul> <b><a name="DB_LOCK_PUT">DB_LOCK_PUT</a></b><ul compact><li>The lock to which the <b>lock</b> structure field refers is released. The <b>locker</b> parameter, and <b>mode</b> and <b>obj</b> fields are ignored.</ul> <b><a name="DB_LOCK_PUT_ALL">DB_LOCK_PUT_ALL</a></b><ul compact><li>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 DB_ENV->lock_vec which appear before the DB_LOCK_PUT_ALL operation are released; those acquired in operations appearing after the DB_LOCK_PUT_ALL operation are not released.</ul> <b><a name="DB_LOCK_PUT_OBJ">DB_LOCK_PUT_OBJ</a></b><ul compact><li>All locks held on <b>obj</b> are released. The <b>locker</b> parameter and the <b>lock</b> and <b>mode</b> structure fields are ignored. Locks acquired in operations performed by the current call to DB_ENV->lock_vec that appear before the DB_LOCK_PUT_OBJ operation are released; those acquired in operations appearing after the DB_LOCK_PUT_OBJ operation are not released.</ul> <b><a name="DB_LOCK_TIMEOUT">DB_LOCK_TIMEOUT</a></b><ul compact><li>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.</ul> <br> <b>DB_LOCK <a name="lock">lock</a>;</b><ul compact><li>A lock reference.</ul> <b>const lockmode_t <a name="mode">mode</a>;</b><ul compact><li>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: <br> <b><a name="DB_LOCK_READ">DB_LOCK_READ</a></b><ul compact><li>read (shared)</ul> <b><a name="DB_LOCK_WRITE">DB_LOCK_WRITE</a></b><ul compact><li>write (exclusive)</ul> <b><a name="DB_LOCK_IWRITE">DB_LOCK_IWRITE</a></b><ul compact><li>intention to write (shared)</ul> <b><a name="DB_LOCK_IREAD">DB_LOCK_IREAD</a></b><ul compact><li>intention to read (shared)</ul> <b><a name="DB_LOCK_IWR">DB_LOCK_IWR</a></b><ul compact><li>intention to read and write (shared)</ul> <br> <p>See <a href="../api_c/env_set_lk_conflicts.html">DB_ENV->set_lk_conflicts</a> and <a href="../ref/lock/stdmode.html">Standard Lock Modes</a> for more information on the lock conflict matrix.</p></ul> <b>const DBT <a name="obj">obj</a>;</b><ul compact><li>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.</ul> <b>u_int32_t timeout;</b><ul compact><li>The lock timeout value.</ul> <br></ul> <b>nlist</b><ul compact><li>The <b>nlist</b> parameter specifies the number of elements in the <b>list</b> array.</ul> <br> <br><b>Errors</b> <p>The DB_ENV->lock_vec method may fail and return one of the following non-zero errors:</p> <br> <b>DB_LOCK_DEADLOCK</b><ul compact><li>A transactional database environment operation was selected to resolve a deadlock.</ul> <b>DB_LOCK_NOTGRANTED</b><ul compact><li>A Berkeley DB Concurrent Data Store database environment configured for lock timeouts was unable to grant a lock in the allowed time.</ul> <br> <br> <b>DB_LOCK_NOTGRANTED</b><ul compact><li>The <a href="../api_c/lock_vec.html#DB_LOCK_NOWAIT">DB_LOCK_NOWAIT</a> flag or lock timers were configured and the lock could not be granted before the wait-time expired.</ul> <br> <br> <b>EINVAL</b><ul compact><li>An invalid flag value or parameter was specified.</ul> <br> <br> <b>ENOMEM</b><ul compact><li>The maximum number of locks has been reached.</ul> <br> <hr size=1 noshade> <br><b>Class</b> <a href="../api_c/env_class.html">DB_ENV</a>, <a href="../api_c/lock_class.html">DB_LOCK</a> <br><b>See Also</b> <a href="../api_c/lock_list.html">Locking Subsystem and Related Methods</a> </tt> <table width="100%"><tr><td><br></td><td align=right> <a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a> </td></tr></table> <p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> </body> </html>