RDF/IMP and IMPX System Management Manual (RDF 1.3+)

Introducing RDF
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
1-2
RDF Subsystem Overview
There are two versions of the RDF product:
1. RDF/IMP (product number T0346), which provides online product initialization,
triple contingency support, subvolume- and file-level replication, online dumping
with updaters running, and SQL big files support.
2. RDF/IMPX (product numbers T0346 and T0347), which provides the same
functionality as RDF/IMP, but with online database synchronization, replication of
auxiliary audit trails, support for network transactions, and lockstep operation.
Note that RDF/IMP and IMPX run on either K-series or S-series systems.
Before reading further in this manual, you should be familiar with the concepts,
terminology, and functions of the NonStop™ TM/MP product and the TMF subsystem.
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
NonStop™ Transaction Manager/MP (TM/MP).
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(s).
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.