VMS Help RECOVER, Qualifiers, /BACKWARD  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Rolls a file backward to a previous state. Use the /BACKWARD
    qualifier to recover a file using a journal that has before-image
    journal entries for the data file that you specify.

    To specify a date and time to which the file is to be rolled
    backward, use the /UNTIL qualifier. You should normally use this
    qualifier for before-image recovery; if you do not use the /UNTIL
    qualifier when you specify the /BACKWARD qualifier, the file is
    automatically rolled back to the time when the first entry was
    made in your before-image journal.

    The file is rolled back using the before-image journal that was
    specified when the file was marked for journaling with the SET
    FILE/BI_JOURNAL command. You can override this default by using
    the /JOURNAL qualifier.

    You must always specify either the /BACKWARD or the /FORWARD
    qualifier, but you cannot specify both.

    When you use before-image recovery for a file that also uses
    recovery unit journaling, the RMS Recovery Utility ensures
    that the data consistency provided by recovery unit journaling
    is maintained. The before-image journal includes records of a
    transaction being started, prepared, committed, or aborted.

    If you use the RECOVER/BACKWARD command to roll back a file that
    is also marked for recovery unit journaling, the file is rolled
    back and includes modifications for all transactions that were
    completed (committed) on or before the ending time of the before-
    image recovery, as follows:

    o  If, at the time before-image recovery is to end, there are no
       active transactions, then before-image recovery takes place in
       the same way as when there is no recovery unit journaling.

    o  If one or more transactions are active at the time before-
       image recovery is to end, only those modifications made within
       transactions that were completed (committed) on or before the
       ending time are included in the file.

       For example, suppose you issue the command RECOVER/BACKWARD
       /UNTIL=10:30 for a file marked for both before-image and
       recovery unit journaling. When before-image recovery is
       complete, the rolled-back file will include all modifications
       that were made within those transactions that completed on or
       before 10:30.

    o  If you apply before-image recovery to a file that is used in a
       multifile application, then you must use the /UNTIL qualifier
       with the RECOVER/BACKWARD command in order to specify a
       time to which the file is rolled back. You should then roll
       back each of the files in the application to the same time
       specified for the first file. If you do not use the same time
       value for the /UNTIL qualifier, then the modifications for one
       or more transactions may be restored to some of your files,
       but not to others.

       If you attempt to recover a file used in a multifile
       application that uses more than one before-image journal,
       the journals must be recovered in their entirety to assure
       transaction consistency. If you use the /UNTIL qualifier, the
       recovered files may still be inconsistent.

    When the recovery operation is complete, the RMS Recovery Utility
    displays the time of the last record it processed (rolled back).
    This is generally the time of the first record modification
    after the ending time (as specified with the /UNTIL qualifier);
    however, it could be an earlier time if there were one or more
    incomplete transactions at the ending time of the before-
    image recovery. In this case, modifications made within such
    transactions are automatically undone as part of the before-image
    recovery operation, and the time of the last record processed
    would reflect the first record modified within one of those
    transactions.