Berkeley DB: DbEnv::lock_get
Description: Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++

# DbEnv::lock_get |

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    #include <db_cxx.h>

    int
    DbEnv::lock_get(u_int32_t locker, u_int32_t flags,
        const Dbt *obj, const db_lockmode_t lock_mode, DbLock *lock);

# Description

The DbEnv::lock_get method acquires a lock from the lock table, returning information about it in the lock argument.

The locker argument specified to DbEnv::lock_get is an unsigned 32-bit integer quantity. It represents the entity requesting or releasing the lock.

The flags value must be set to 0 or the following value:

DB_LOCK_NOWAIT
  If a lock cannot be granted because the requested lock conflicts with an existing lock, return immediately instead of waiting for the lock to become available.

The obj argument is an untyped byte string that specifies the object to be locked or released.

The mode argument is an index into the environment's lock conflict array. See DbEnv::set_lk_conflicts and Standard Lock Modes for a description of that array.

The DbEnv::lock_get method may return or throw an exception encapsulating one of the following values:

DB_LOCK_NOTGRANTED
  A lock was requested that could not be immediately granted and the flags parameter was set to DB_LOCK_NOWAIT.

Otherwise, the DbEnv::lock_get method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success.

# Errors

The DbEnv::lock_get method may fail and throw an exception or return a non-zero error for the following conditions:

DB_LOCK_DEADLOCK
  The operation was selected to resolve a deadlock.

EINVAL
  An invalid flag value or parameter was specified.

ENOMEM
  The maximum number of locks has been reached.

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. If a catastrophic error has occurred, the DbEnv::lock_get method may fail and either return DB_RUNRECOVERY or throw an exception encapsulating DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.

### Classes

DbEnv, DbLock

# See Also

DbEnv::set_lk_conflicts, DbEnv::set_lk_detect, DbEnv::set_lk_max, DbEnv::lock_detect, DbEnv::lock_get, DbEnv::lock_id, DbLock::put, DbEnv::lock_stat and DbEnv::lock_vec.`

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