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