VMS Help RMS, $SPACE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The Space service lets you space (skip) a tape file forward or
    backward a specified number of blocks.

                         RAB64 USERS (ALPHA ONLY)

       On Alpha systems, RAB64 can replace the RAB or RAB prefix
       wherever it is used with the Space service on OpenVMS Alpha
       systems.

    Format

      SYS$SPACE  rab [,[err] [,suc]]

  Additional Information (explode) :

• Returns
• Arguments
• Condition Values Returned