# DbEnv::set_data_dir

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    #include <db_cxx.h>

    int
    DbEnv::set_data_dir(const char *dir);

# Description

Set the path of a directory to be used as the location of the access method database files. Paths specified to the Db::open function will be searched relative to this path. Paths set using this interface are additive, and specifying more than one will result in each specified directory being searched for database files. If any directories are specified, created database files will always be created in the first path specified.

If no database directories are specified, database files can exist only in the environment home directory. See Berkeley DB File Naming for more information.

For the greatest degree of recoverability from system or application failure, database files and log files should be located on separate physical devices.

The DbEnv::set_data_dir method configures operations performed using the specified DbEnv handle, not all operations performed on the underlying database environment.

The DbEnv::set_data_dir interface may not be called after the DbEnv::open interface is called. If the database environment already exists when DbEnv::open is called, the information specified to DbEnv::set_data_dir must be consistent with the existing environment or corruption can occur.

The DbEnv::set_data_dir 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.

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

# Errors

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

EINVAL
  An invalid flag value or parameter was specified.

  Called after DbEnv::open was called.

The DbEnv::set_data_dir 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::set_data_dir method may fail and either return DB_RUNRECOVERY or throw a DbRunRecoveryException, in which case all subsequent Berkeley DB calls will fail in the same way.

# Class

DbEnv

# See Also

Database Environments and Related Methods`

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