Library Version 18.1.40

DbEnv::mutex_set_align()
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## DbEnv::mutex_set_align()

    #include <db_cxx.h>

    int
    DbEnv::mutex_set_align(u_int32_t align);

Set the mutex alignment, in bytes.

It is sometimes advantageous to align mutexes on specific byte boundaries in order to minimize cache line collisions. The `DbEnv::mutex_set_align()` method specifies an alignment for mutexes allocated by Berkeley DB.

The database environment's mutex alignment may also be configured using the environment's DB_CONFIG file. The syntax of the entry in that file is a single line with the string "mutex_set_align", one or more whitespace characters, and the mutex alignment in bytes. Because the DB_CONFIG file is read when the database environment is opened, it will silently overrule configuration done before that time.

The `DbEnv::mutex_set_align()` method configures a database environment, not only operations performed using the specified DbEnv handle.

The `DbEnv::mutex_set_align()` method may not be called after the DbEnv::open() method is called. If the database environment already exists when DbEnv::open() is called, the information specified to `DbEnv::mutex_set_align()` will be ignored.

The `DbEnv::mutex_set_align()` 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

#### align

The align parameter is the mutex alignment, in bytes. The mutex alignment must be a power-of-two.

### Errors

The `DbEnv::mutex_set_align()` method may fail and throw a DbException exception, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:

#### EINVAL

If the method was called after DbEnv::open() was called; or if an invalid flag value or parameter was specified.

### Class

DbEnv

### See Also

Mutex Methods

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