SQL/MP Installation and Management Guide

Performing Recovery Operations
HP NonStop SQL/MP Installation and Management Guide—523353-004
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File Recovery With the TIME Option
File Recovery With the TIME Option
By using the file recovery feature with the TIME option, you can resolve several
different kinds of problems:
•
If a database object is purged by accident, you can use the TIME option to recover
the object's file as it existed just prior to the purge. This action effectively recovers
the entire file but not the catalog definition of the object.
•
If an application error updates the database in an inconsistent way, you can
recover the database to the state it was in at a specified time before the error
occurred.
•
If a licensed SQLCI2 or CLEANUP operation incorrectly alters or damages the
database or catalogs, you can recover the database or catalogs to their previous
state.
•
If you have a saved test database or starting database, you can recover that
database to the same point many times. Suppose that in your testing procedures
you need to always start with the same database. This database can be loaded to
the node or recovered by using TMF file recovery with the TIME option.
Using file recovery with the TIME option can be difficult, however, because this method
requires you to coordinate recovery of interrelated objects, such as tables and their
indexes.
For more information about using file recovery with the TIME option, see the TMF
Operations and Recovery Guide.
Recovering Purged SQL Tables
There are two ways of using TMF to recover an SQL table that was accidentally
purged:
•
Use file recovery to recover the catalog and the purged table. This approach works
adequately only if no updates were applied to the catalog after the table was
purged (which is usually not the case).
•
Re-create the table to put the entry back into the catalog, and then recover the
table and update the creation and redefinition timestamps in the catalog (if
needed).
Caution. The TMF subsystem carries no information about the relationships between file
labels and catalogs. If a table is dropped, for example, file recovery cannot restore the catalog
entries for the table. If the file recovery operation starts at a time just before a table was
dropped, you might lose subsequent DDL changes.