Introduction to Data Management

Protecting Databases With RDF
8-4 15873 Tandem Computers Incorporated
Accessible Operating
Information
Through RDFCOM and another utility called RDFSCAN, you can access valuable
status information. For example, you can find out what portion of the extracted
records from the primary database has been transmitted to the backup system. You
can determine what portion of the records received on the backup system has been
applied to the backup database.
Relationship to Other
Products
RDF is based upon, and uses, routines that are part of TMF. RDF relies upon these
TMF routines for transaction backout, autorollback, rollforward, and concurrency
control, described in the previous section.
RDF Components RDF includes the following major components: the RDFCOM utility, the RDFSCAN
utility, and operating processes on the primary and backup systems.
RDFCOM Utility The RDFCOM utility program enables you to enter commands for controlling RDF.
Most of these commands access the RDF configuration file, which defines operating
parameters for RDF. This file contains global parameters that apply to all of RDF,
specifying such information as operating mode selection (online or archive),
destination file and device for logging information, and backup system name. It also
contains parameters that apply to individual RDF processes, such as primary and
backup CPU, execution priority, and disk volumes available to the process. The
configuration file is originally created on the primary system, but is later copied to the
backup system and maintained on both systems.
The RDFCOM commands request such functions as:
Specifying, adding, altering, displaying, and deleting parameter values in the
configuration file
Copying the current configuration file from the primary to the backup system, to
provide a backup copy of this file
Starting and stopping RDF processes
Dynamically enabling and disabling database updating on the backup system
Directing the backup database to take over from the primary database
You can enter RDFCOM commands either interactively or through a command (EDIT)
file. When you use RDFCOM interactively, you can access the services of an online
help facility. Typically, you run RDFCOM from the backup system, specifying the
primary system in the logon command.
RDFSCAN Utility When you install RDF on the primary and backup systems, a log file is created on
both of these systems to record special events. RDF processes write information to the
log file when they are started and stopped, when exception records are produced, and
when RDF issues informational or warning messages. RDF also displays this
information on an online log device. System managers and operators can use
RDFSCAN to read the information in the log file.