The RMU Restore Only_Root command rebuilds only the database root
    (.rdb) file from a backup file, produced earlier by an RMU Backup
    command, to the condition the .rdb file was in when the backup
    operation was performed. Use the command qualifiers to update
    the .rdb file. The area qualifiers alter only the .rdb file, not
    the storage areas themselves. Use the area qualifiers to correct
    the restored backup root file so that it contains storage area
    information that was updated since the last backup operation was
    performed on the database. This is useful when you need to match
    the root from an older backup file of your database with the area
    information in the more recent backup file of your database in
    order to have a usable database.

    When the .rdb file is restored by itself, be sure that you
    correctly set the transaction state of the database with the
    Initialize_Tsns qualifier or the Set_Tsn qualifier. If the
    database transaction sequence number (TSN) and commit sequence
    number (CSN) are not set to the same values as those that were
    in the lost .rdb file, there will be an inconsistency in the
    journaling if after-image journaling is enabled. Therefore, you
    cannot recover the database by using journal files created before
    you used either the Initialize_Tsns qualifier or the Set_Tsn
    qualifier in a restore-only-root operation.

    You should set the TSN to a value equal to or greater than the
    value that was in the lost .rdb file. If the TSN is set to a
    lower value than the value stored in the lost database root file,
    the database is corrupted, and it might return incorrect data or
    result in application failures. If the number you have selected
    is less than the Next CSN and Next TSN values, you will receive a
    fatal error message as follows:

    %RMU-F-VALLSSMIN, value (0:40) is less than minimum allowed
     value (0:74) for Set_Tsn=tsn

    After the set TSN and reinitialize TSN operations
    complete, and after you have verified the .rdb
    file, enabled after-image journaling, and the
    new .aij file is created, all .aij records are based on the new
    starting TSN and CSN numbers in the .rdb file.

    Although Oracle Corporation recommends that your backup strategy
    ensures that you maintain a current full and complete database
    backup file, it is possible to restore the database from
    current full by-area backup files only. This is accomplished by
    restoring the root and specifying the Noupdate_Files and Noset_
    Tsn qualifiers. When you specify the Noset_Tsn qualifier, the
    TSN and CSN values on the restored database will be the same as
    those recorded in the backup file. When you specify the Noupdate_
    Files qualifier, the database root is restored but RMU Restore
    Only_Root will not link that restored root to any of the area
    files, nor will it create or update the snapshot (.snp) files. By
    specifying the Noupdate_Files and Noset_Tsn qualifiers with the
    RMU Restore Only_Root command, you can use the following strategy
    to restore your database:

    1. Restore the root from the most recent full by-area backup
       file.

    2. Restore the storage areas by applying the by-area backup files
       in reverse order to their creation date.

       Apply the most recent by-area backup file first and the oldest
       by-area backup file last. (Be sure you do not restore any area
       more than once.)

    3. Recover the database by applying the after-image journal
       (.aij) files.

       You can recover the .aij files manually by using the RMU
       Recover command. Or, if the state of your .aij files permits
       it, you can allow RMU Restore Only_Root to automatically
       recover the .aij files by not specifying the Norecovery
       qualifier with the last RMU Restore command you issue. For
       details on the automatic recovery feature of the RMU Restore
       command, see the help entry for the RMU Restore command.
       (The automatic recovery feature is not available for the RMU
       Restore Only_Root command.)

    When you use this strategy, be sure that the first RMU Restore
    command after the RMU Restore Only_Root command includes the
    most recent RDB$SYSTEM storage area. The RDB$SYSTEM storage area
    contains the structures needed to restore the other database
    storage areas. For this reason, Oracle Corporation suggests that
    you back up the RDB$SYSTEM storage area in every by-area backup
    operation you perform.

    See Example 6 in the Examples help entry under this command for a
    demonstration of this method.

    Note that the database backup file must be recent-differences
    between the database and backup file must be known, and the
    number of storage areas must be unchanged since the backup file
    was created. If you have moved a storage area, use the File
    qualifier to show its new location and the Snapshot qualifier
    to indicate the current version of the area's .snp file.

                                   NOTE

       You must perform a full and complete backup operation
       on your database when the RMU Restore Only_Root command
       completes. Oracle Corporation recommends that you define a
       new after-image journal configuration with the RMU Restore
       Only_Root command by using either the After_Journal or the
       Aij_Options qualifier. This action ensures that the new
       .aij file can be rolled forward in the event that another
       database restore operation becomes necessary.