This specifies the directory service to use as the default, when the
 command does not specify a directory service.

     DIRECTORY_SERVICE dir-service

 The service must be one of:

     DIRECTORY_SERVICE LOCAL
     DIRECTORY_SERVICE DECDNS
     DIRECTORY_SERVICE PHASEIV

 If other parameters are specified in the command, this also determines
 the directory service that those additional default value parameters
 apply to.  For example:

     SET DEFAULT DIRECTORY_SERVICE DECdns REVERSE_DIR .DNA_BackTranslation