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

Managing RDF
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
5-7
Processor Failures
If any RDF process pair stops unexpectedly, the monitor sends an abort message to all
other RDF processes.
The subtopics that follow discuss how RDF responds to extractor, receiver, updater, and
RDF state transition failures.
Extractor Failure
Although the extractor runs as a process pair, the primary process does not maintain
restart information nor checkpoint this information to its backup. Instead, the receiver
maintains all restart information for the extractor, ensuring that the extractor is
restartable. The restart point is based on the Master Audit Trail (MAT) position of the
last record stored in the image trail on the backup system.
If the extractor process pair inadvertently stops, the monitor sends abort messages to the
other RDF processes in order to bring about an orderly shutdown of RDF. You can then
restart the subsystem by merely issuing a START RDF command.
If the primary extractor process fails, the backup process requests from the receiver a
new starting position in the MAT, ensuring a correct restart position. This extractor-
receiver protocol also provides protection against messages from the extractor
erroneously arriving out-of-order: if a message arrives out-of-order, the receiver simply
directs the extractor to restart. When the primary CPU that failed comes back up, RDF
switches the new primary (formerly the backup) extractor process so that it runs in the
primary CPU.
Receiver Failure
If the primary receiver process stops, the backup receiver process takes over and
resynchronizes with the extractor process. The extractor process might have to resend
audit data that was generated several seconds earlier. When the primary CPU that failed
comes back up, RDF switches the new primary (formerly the backup) receiver process
so that it runs in the primary CPU.
Note. If the monitor process pair unexpectedly stops (for example, as in a double CPU failure),
you must stop the other RDF processes manually and then restart the subsystem. When
stopping RDF processes manually, you must first stop the extractor on the primary system,
then stop all updaters on the backup system, and finally stop the receiver on the backup
system. The easiest way to do this is to issue a series of commands of the following form:
STATUS *,PROG $SYSTEM.RDF.procname, STOP. The following command provides an
example:
STATUS *, PROG $SYSTEM.RDF.RDFUPDO, STOP
Alternatively, after stopping the extractor, you can stop all updaters and the receiver on the
backup system by issuing a STOP RDF command on the backup system.
Caution. During the interval between loss of the extractor and RDF subsystem restart, you
should not add any disk volumes to the RDF configuration (with the ADD VOLUME command).