# Berkeley DB: DbEnv::mutex_lock
Berkeley DB: An embedded database programmatic toolkit.
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### DbEnv::mutex_lock

`

###

    #include <db_cxx.h>

    int
    DbEnv::mutex_lock(db_mutex_t mutex);

### Description: DbEnv::mutex_lock

The DbEnv::mutex_lock method locks the mutex allocated by DbEnv::mutex_alloc. The thread of control calling DbEnv::mutex_lock will block until the lock is available.

The DbEnv::mutex_lock method may not be called before the DbEnv::open method has been called.

The DbEnv::mutex_lock 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.

### Parameters

mutex
  The mutex parameter is a mutex previously allocated by DbEnv::mutex_alloc.

### Errors

The DbEnv::mutex_lock method may fail and throw DbException, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:

EINVAL
  An invalid flag value or parameter was specified.

### Class

DbEnv

### See Also

Database Environments and Related Methods`

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