Rdf Subsystem Overview - HP NonStop RDF J-series RVUs Management Manual

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 records associated
with volumes protected by RDF to RDF receiver processes on the backup system. Each receiver
process sorts the audit records 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 records 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.
32 Introducing RDF