RDF System Management Manual for H-Series RVUs (RDF 1.8)

Integrity NonStop NS-series servers running RDF 1.8. For information about subsystem
interoperability as it relates to your particular version of the RDF subsystem, read the software
documentation supplied with your RDF software.
Before reading further in this manual, you should be familiar with the concepts, terminology,
and functions of the NonStop TMF product. You should know about the objects on which TMF
operates, such as transactions, audit trails, and audit volumes. You should understand how
TMF software uses elements like before-images, after-images, and control records. In addition,
you should also understand the TMF processes that perform backout, volume recovery, and
file recovery. If you are not familiar with this information, you should read TMF Introduction.
RDF Subsystem Overview
RDF maintains a logically replicated database on one or more backup systems by monitoring
changes made to audited tables and files on designated primary system volumes and applying
those changes to corresponding volumes on the backup system. Although logically the same as
the primary database, a backup database is not an actual physical copy. For those volumes
designated to be protected by RDF, the backup database contains the same data for all committed
transactions as in the primary database.
On the primary system, RDF extractor processes read audit trails (logs maintained by TMF of
all database transactions that affect audited tables and files), and send all audit information
associated with volumes protected by RDF to RDF receiver processes on the backup system.
Each receiver process sorts the audit information and writes it to the appropriate image trail.
RDF updater processes on the backup system read their image trails and apply the changes to
the backup database. An RDF purger process on the backup system interacts with the updaters
to determine when image files can be purged.
Each volume protected by RDF on the primary system has its own updater process on the backup
system responsible for applying audit information to the corresponding volume on the backup
system.
Figure 1-1 illustrates a basic RDF configuration that protects data volumes configured to a Master
Audit Trail (MAT) and an auxiliary audit trail.
36 Introducing RDF