/sys$common/syshlp/helplib.hlb SET, FILE, /AI_JOURNAL, Keywords  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Four keywords are used as parameters to the SET FILE/AI_JOURNAL
    command: ALLOCATION, [NO]CREATE, EXTENSION, and FILE. You
    must always use the FILE keyword; you can also use any, all, or
    none of the other three keywords.

    Use an equal sign (=)  immediately after the SET FILE/AI_JOURNAL
    command to use a keyword. If you use more than one of the
    keywords, enclose the list in parentheses and separate the items
    in the list with commas.

 ALLOCATION=n

    Specifies the initial size, in blocks, of the journal. The
    ALLOCATION keyword is meaningful only when the CREATE keyword
    is also used.

    The default allocation is 0 blocks.

 CREATE

    Specifies that a new journal is to be created. If no journal
    exists, using this keyword creates a new one. If a journal (with
    the file specification given in this command) already exists,
    using this keyword creates a new version of the journal. In the
    latter instance, the data file named in this SET FILE command
    is journaled to the new journal. Any other files that are being
    journaled to the previous version of the journal will continue to
    be journaled to that previous version.

    If a journal does not already exist, be sure to use the CREATE
    keyword with the SET FILE/AI_JOURNAL command. If you do not
    specify the CREATE keyword and the file that you specify with
    the FILE keyword does not exist, a journal will not automatically
    be created and an error message is displayed.

    When you create a journal for after-image journaling, the file
    protection for the journal is determined as follows:

    o  If a version of the journal that you specify with the CREATE
       keyword already exists, then the new version of the journal
       has the same file protection and access control list (ACL) as
       the most recent version.

    o  If there is no existing journal (that is, if you are creating
       version 1 of the journal), then the file protection and
       ACL of the journal are the default file protection for the
       process that creates the journal, except that none of the four
       ownership categories (system, owner, group, world) is given
       delete access.

    Also, every time that you use the CREATE keyword, be sure to make
    a backup copy of the data file. (If it is the first time that
    the data file is marked for after-image journaling, then you must
    make a backup copy of the data file, regardless of whether the
    CREATE keyword is used.)

                                   NOTE

       To be able to recover the data file at a later time, you
       must mark the file for journaling, and then make a backup
       copy of the data file, even if it contains no data.

    In most cases (in particular, when you are using after-image
    journaling to protect against loss of data from a device
    failure), you should keep the backup copy on a different volume
    from the data file. If recovery becomes necessary, you will be
    able to perform after-image recovery only if a backup copy of the
    data file is available.

    If you want to use a single journal for both after-image and
    before-image journaling, do not use the CREATE keyword with both
    the /AI_JOURNAL and /BI_JOURNAL qualifiers, because that will
    create two separate journals. When you create a journal that
    will be used for more than one data file or more than one type
    of journaling (after-image or before-image), you should first
    use a SET FILE command to create the journal for a single type
    of journaling and for a single data file. After the journal is
    created, then you can use a single SET FILE command for multiple
    data files and both after-image and before-image journaling. For
    example, you might use the following sequence of commands:

    $ SET FILE/AI_JOURNAL=(FILE=JNL_DISK:,CREATE) [WEEKLY]SALES.DAT
    $ SET FILE/BI_JOURNAL=(FILE=JNL_DISK:[WEEKLY]SALES) -
    _$INVOICES.DAT,COMMISSIONS.DAT

 EXTENSION=n

    Specifies the default extension quantity, in blocks, for the
    journal. You can specify a value from 0 to 65,535.

    The EXTENSION keyword is meaningful only when you use the
    CREATE keyword. If the file is extended, the value that you
    specify is used. If you do not use the EXTENSION keyword
    when you create a journal, RMS calculates its own EXTENSION
    value for the journal.

 FILE=journal-filespec

    Specifies the journal where all modifications to the named data
    file will be recorded. The default file specification for the
    journal is the file specification of the data file that you name,
    but with a file type of RMS$JOURNAL. If you provide a partial
    file specification for the journal, any unspecified portions are
    taken from the default file specification. The FILE keyword is
    required when you use the SET FILE/AI_JOURNAL command.

    If you are using after-image journaling to protect against the
    loss of data due to a device failure (such as a head crash),
    you should keep the journal on a different volume from the
    one on which the data file is kept. Only by keeping the data
    file and journals on separate volumes can you use after-image
    recovery to restore the data file if its recording medium becomes
    corrupted (for example, by a disk head crash). If you issue the
    SET FILE/AI_JOURNAL command and the journal is on the same volume
    as the data file being marked for after-image journaling, the
    INVAIJDEV warning message is issued.

    The file specification cannot include a node name, since the SET
    FILE command is not valid for network access.

    You can use a single journal for multiple data files for after-
    image journaling, and you can also use a single journal for both
    after-image and before-image journaling.