RDF System Management Manual (RDF 1.6)

Introducing RDF
HP NonStop RDF System Management Manual—529826-002
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RDF Subsystem Overview
There are two versions of the RDF product:
1. RDF/IMPX (product numbers T0346 and T0347) provides online product
initialization, online database synchronization, triple contingency support,
subvolume-level and file-level replication, stop-update-to-time (for quiescing the
backup database to a stable state), NonStop SQL/MP big files support, replication
of auxiliary audit trails, support for network transactions, lockstep operation, and
many other features.
2. RDF/ZLT (product number T0618), which requires that RDF/IMPX be installed,
provides zero lost transaction (ZLT) protection using mirrored disks.
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 the Introduction to the HP NonStop
Transaction Management Facility (TMF).
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.