#include <db_cxx.h> int DbEnv::set_lg_dir(const char *dir);
The path of a directory to be used as the location of logging files. Log files created by the Log Manager subsystem will be created in this directory.
If no logging directory is specified, log files are created 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 database environment's logging directory 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 "set_lg_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. Note that if you use this method for your application, and you also want to use the db_recover, db_printlog, db_archive, or db_log_verify utilities, then you should set create a DB_CONFIG file and set the "set_lg_dir" parameter in it.
         The DbEnv::set_lg_dir() method configures operations performed using
         the specified DbEnv 
         handle, not all operations performed on the underlying database
         environment.
    
         The DbEnv::set_lg_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::set_lg_dir() must be consistent with
         the existing environment or corruption can occur.
    
         The DbEnv::set_lg_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::set_lg_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.