Sets or clears the default transaction of the calling process.

    Format

      SYS$SET_DEFAULT_TRANS  [efn] ,[flags] ,iosb [,[astadr]

                             ,[astprm] ,[new_tid] ,[old_tid]]

    C Prototype

      int sys$set_default_trans  (unsigned int efn, unsigned int

                                 flags, struct _iosb *iosb,...);