SQL/MX 2.x Installation and Management Guide (G06.24+, H06.03+)

Performing Recovery Operations
HP NonStop SQL/MX Installation and Management Guide—523723-004
12-2
Recovering Disk Volumes
•
Use the file recovery method with a specified TIME option to recover a database to
a given consistent time, as described in Recovering Files With the TIME Option on
page 12-3.
Recovering Disk Volumes
TMF volume recovery is invoked automatically by the START TMF command and is
invoked as needed thereafter when a volume becomes accessible. Volume recovery
uses the audit trails to roll back incomplete transactions and return the database to the
last consistent state.
Volume recovery might fail to recover a volume or a file. Possible recoverable cases
are:
•
A volume becomes unavailable during the volume recovery operation. When you
bring up the volume, TMF automatically restarts volume recovery.
•
A file is corrupted or inconsistent in such a way that volume recovery cannot apply
the audit trail information. If volume recovery fails to recover a file, FILEINFO
displays REDONEEDED and UNDONEEDED flags. For views, tables, indexes,
and ENSCRIBE files, the information appears after the modification timestamp of
the table.
Normally, volume recovery recovers such files when the volume is started for
transaction processing. If, however, the volume is already started and the file is still
marked with REDONEEDED or UNDONEEDED, you must recover the file by using
file recovery.
Recovering Files
File recovery is usually the method to use if other recovery methods fail. Use file
recovery only if you consistently dump audit trails to tape and make online dumps. File
recovery reconstructs an audited file from the initial starting point of the online dumps
and applies all the changes to the file from the history of the audit trails. The file is
recovered to the last consistent point in the database. These guidelines apply:
•
Invoke the file recovery process by issuing the RECOVER FILES command to a
TMF interface such as TMFCOM. The process prompts the operator for the online
dumps and audit-trail tapes as needed. Audit trails that still reside on disk are read
directly from disk.
•
If you do not specify the FROMARCHIVE option in the RECOVER FILES
command, file recovery recovers only files marked undo-needed. If you specify the
FROMARCHIVE option of the RECOVER FILES command, file recovery attempts
to recover the entire file set, regardless of the setting of the redo-needed and
undo-needed flags.
•
The file recovery process cannot recover a file that did not exist at the time of an
online dump. The process cannot perform a create function. You must perform an