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

Planning Database Security and Recovery
HP NonStop SQL/MX Installation and Management Guide—523723-004
5-21
Using RDF to Set Up a Backup System
Using RDF to Set Up a Backup System
The RDF subsystem monitors changes made to a production database on a local
(primary) system and maintains a copy of that database on a remote (backup) system.
Because it applies changes to the backup database as soon as they are detected on
the primary system, the RDF subsystem keeps the backup database continuously up
to date with changes made by business applications on the primary system. You are
able, therefore, to switch your business operations from the primary system to the
backup system with minimal interruption and loss of data in the event of unexpected or
planned outages of the primary system.
The RDF subsystem also enables you to use the backup database as a read-only
resource to balance the overall workload and improve response times. Activities at the
backup system can include querying the database, processing heavy batch-reporting
loads, and consolidating data from multiple sites into one central site. For more
information, see the RDF System Management Manual.
RDF configuration enables users to map volumes on the primary node to different
volumes on the RDF backup node. Except for this volume-to-volume mapping, the rest
of the primary and backup file names must match exactly. This subsection describes
how to create an RDF backup database with the correct file names, populate the
backup database, and synchronize it with the primary database.
You can create RDF backup databases online or offline. Offline creation uses Backup
and Restore 2 and requires that the primary database be taken offline until the backup
database is created and RDF replication has started. Online creation of the backup
database allows the primary database to remain online while the backup database is
being created and populated.
Online creation uses several methods to create tables on the RDF backup node.
These tables can be populated using INSERT...SELECT. To use this technique, you
must configure either the primary or backup catalog as a remote catalog by using the
SQL/MX distribution REGISTER CATALOG command. Operations such as the
INSERT...SELECT statement need to involve tables from both catalogs. For more
information about INSERT...SELECT, see the example in Section 14, Migrating an
SQL/MP Database to NonStop SQL/MX Release 2.1 or Release 2.0.
Using Guardian Physical Names for SQL/MX Objects
For information about using the MXGNAMES utility with RDF to facilitate the use of
Guardian physical names for SQL/MX objects, see Appendix B, Using Guardian
Names With TMF, RDF, and Measure.
Note. If you run SQL DDL operations with Shared Access on RDF-protected objects, you must
be certain that the operation committed on your primary system before you attempt to perform
the operation on your RDF backup system.