DbEnv::add_data_dir()
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## DbEnv::add_data_dir()

    #include <db_cxx.h>

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

Add 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 method are additive, and specifying more than one will result in each specified directory being searched for database files.

If no database directories are specified, database files must be named either by absolute paths or relative to the environment home directory. See Berkeley DB File Naming for more information.

The database environment's data directories 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 "add_data_dir", one or more whitespace characters, and the directory name.

The `DbEnv::add_data_dir()` method configures operations performed using the specified DbEnv handle, not all operations performed on the underlying database environment.

The `DbEnv::add_data_dir()` 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::add_data_dir()` must be consistent with the existing environment or corruption can occur.

The `DbEnv::add_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.

### Parameters

#### dir

The dir parameter is a directory to be used as a location for database files.

When using a Unicode build on Windows (the default), this argument will be interpreted as a UTF-8 string, which is equivalent to ASCII for Latin characters.

### Errors

The `DbEnv::add_data_dir()` 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

Database Environments and Related Methods

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