VMS Help  —  RMU72  RMU_ERRORS, ALRATTDB
  command not allowed - already attached to a database

  Explanation:  The RMU ALTER ATTACH command is being issued  when
  another database is currently attached.

  User Action:  Issue an RMU ALTER DETACH command to  detach  from
  the  current  database.   Then  reissue  the  RMU  ALTER  ATTACH
  command.
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