recovery unit journals are created by using either the DEVICE or LABEL keyword. Use the DEVICE keyword to specify the location of recovery unit journals using a device name or a logical name. Use the LABEL keyword to specify the location of recovery unit journals using a volume label. You can only use one of these two keywords (LABEL or DEVICE) to specify the recovery unit journal location. In either case, only the volume label is actually stored with the file. At run time, RMS attempts to translate the logical name DISK$volume_label when creating a recovery unit journal. This is the default logical name created by the Mount Utility when you mount the disk using the /SYSTEM or /CLUSTER qualifier. If you do not mount the disk using the /SYSTEM or /CLUSTER qualifier, you must define the logical name DISK$volume_label using the DEFINE command with the /SYSTEM and /EXECUTIVE_MODE qualifiers. You must have the SYSNAM (system logical name) or the SYSPRV (system privilege) privilege to use the /SYSTEM qualifier. NOTE The logical name DISK$volume_label can point to any disk device on the system that is mounted and has for its volume label an executive-mode logical name in the form DISK$volume_label with the concealed and terminal attributes. data-filespec[,...] Specifies the file that is to be marked for recovery unit journaling. If a data file has been marked for recovery unit journaling with this command, DECdtm transaction services ($START_TRANS, $END_TRANS, and $ABORT_TRANS) must be used by an application program to define transactions whenever data in this file is modified. If you specify more than one file, separate the file specifications with commas. The asterisk (*) and the percent sign (%) wildcard characters are allowed. The file specification cannot include a node name, since the SET FILE command is not valid for network access.

8.2  –  Description

    The SET FILE/RU_JOURNAL command marks an RMS file for recovery
    unit journaling. To use recovery unit journaling for a data file,
    a data file must be marked for recovery unit journaling with the
    SET FILE/RU_JOURNAL command, and transactions must be defined
    in an application program using DECdtm transaction services. You
    can also use this command to specify the default volume on which
    recovery unit journals will be created for this file.

    Use the SET FILE/NORU_JOURNAL command to unmark a file for
    recovery unit journaling. After you use the SET FILE/NORU_JOURNAL
    command for a file, modifications to that data file will no
    longer be written to a recovery unit journal.

    If you wish to delete a file that has been marked for recovery
    unit journaling, you must use the SET FILE/NORU_JOURNAL command
    before you can delete the file.

    There is no reason other than performance to keep recovery unit
    journals on a different volume from the file being journaled.
    Unlike after-image journaling, which protects against a system
    failure such as a head crash that causes a loss of data, recovery
    unit journaling ensures that a predefined set of operations are
    either done in their entirety, or not done at all. In the event
    of an abnormal termination of the application, such as a system
    crash or a Ctrl/Y, any incomplete transactions are automatically
    rolled back (undone). Because all recovery unit journals must
    be available before the data files can be rolled back, locating
    recovery unit journals on a volume where availability might be
    low could reduce the availability of the data files that use
    those recovery unit journals.

    Specifying a location for recovery unit journals for a file
    does not guarantee that the recovery unit journals will always
    be located on the named device or volume. For any active
    transaction, there is always only one recovery unit journal for
    local files. Thus, if many files are involved in a transaction, a
    single recovery unit journal is used, even if different locations
    for the journals had been specified (for individual files) with
    different SET FILE/RU_JOURNAL commands.

    Remote files are an exception to this rule. Each remote file
    associated with a transaction has its own recovery unit and
    recovery unit journal. The recovery unit journal resides on the
    remote system. The volume is chosen in the same way as for local
    files. Remote files have no effect in determining where the local
    recovery unit journal resides.

    A journal is not deleted when the transaction has been completed.
    Recovery unit journals are automatically deleted only when
    all of the files involved in the transaction are closed and
    the application exits. RMS journaling automatically creates a
    recovery unit journal at run time, whenever the first record
    stream associates with a transaction. All record streams in
    the process associated with the same transaction share a single
    recovery unit journal. Once a recovery unit journal is created,
    it can be reused for another transaction by the process that
    created it. A recovery unit journal is created only when there is
    no available recovery unit journal opened by the process for the
    current transaction.

8.3  –  Examples

    1.$ SET FILE/RU_JOURNAL FINANCE_DISK:[PAYROLL]WEEKLY.DAT

      This command marks the file WEEKLY.DAT for recovery unit
      journaling. Any operation within an application that modifies
      this file must be in a defined transaction (defined by DECdtm
      transaction services).

    2.$ SET FILE/AI_JOURNAL=(FILE=JNL_DISK:, CREATE)-
      _$ /RU_JOURNAL/LOG OVERDUE.DAT
      %SET-I-JCREATED, journal JNL_DISK:[PAYABLE]OVERDUE.RMS$JOURNAL;1
      created
      %SET-I-FILMARKAI, WORK_DISK:[PAYABLE]OVERDUE.DAT;1 marked for RMS
      after-image journaling
      -SET-I-JFILE, using journal JNL_DISK:[PAYABLE]OVERDUE.RMS$JOURNAL;1
      %SET-I-FILMARKRU, WORK_DISK:[PAYABLE]OVERDUE.DAT;1 marked for RMS
      recovery-unit journaling
      %SET-I-MODIFIED, WORK_DISK:[PAYABLE]OVERDUE.DAT;1 modified

      $ SET FILE/AI_JOURNAL=(FILE=JNL_DISK:OVERDUE)-
      _$ /RU_JOURNAL/LOG  CURRENT.DAT

      %SET-I-FILMARKAI, WORK_DISK:[PAYABLE]CURRENT.DAT;1 marked for RMS
      after-image journaling
      -SET-I-JFILE, using journal JNL_DISK:[PAYABLE]OVERDUE.RMS$JOURNAL;1
      %SET-I-FILMARKRU, WORK_DISK:[PAYABLE]CURRENT.DAT;1 marked for RMS
      recovery-unit journaling
      %SET-I-MODIFIED, WORK_DISK:[PAYABLE]CURRENT.DAT;1 modified

      In this example, the files OVERDUE.DAT and CURRENT.DAT are
      marked for after-image and recovery unit journaling using two
      SET FILE commands. In this example, a single journal (JNL_
      DISK:[PAYABLE]OVERDUE.RMS$JOURNAL) is used for after-image
      journaling.

      The first SET FILE command uses the /CREATE
      qualifier to create a new after-image journal, JNL_
      DISK:[PAYABLE]OVERDUE.RMS$JOURNAL, for the file OVERDUE.DAT.
      The file specification uses the current default directory
      [PAYABLE] and the default file extension RMS$JOURNAL.

      The second SET FILE command marks the file CURRENT.DAT for
      after-image and recovery unit journaling, checks the disk JNL_
      DISK to see whether an after-image journal already exists, and
      uses the existing journal JNL_DISK:[PAYABLE]OVERDUE.RMS$JOURNAL
      for the file CURRENT.DAT.