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

Managing RDF
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
5-8
TMF Audited Volume Crash
Updater Failure
If an updater process fails, RDF aborts. A subsequent START RDF command restarts
this process without requiring database resynchronization. To support restartability,
however, the updaters use a different mechanism than the extractor or receiver do: the
updaters rely entirely on context saving rather than checkpointing. For this reason, if the
backup member of an updater process pair takes over because the CPU of the primary
member failed, the backup updater might have to start at an earlier point in the image
trail and require several minutes to reach the point where the primary process was
positioned when the CPU failed.
When a primary CPU on which an updater process is running goes down and then
comes back up, RDF does not switch the updater to run on the reactivated primary CPU.
Instead, once the backup updater takes over, it becomes (and remains) the new primary
process. If you stop and then restart updating, however, the original CPU configuration
for this updater process is restored.
RDF State Transition Failure
Periods during which the RDF updating facility, or RDF itself, is either starting or
stopping are known as RDF state transitions. In rare instances, when a primary CPU
fails for an RDF process during execution of a STOP RDF or STOP UPDATE
command, not all RDF processes complete the state transition properly.
To minimize the chance of encountering this kind of failure, avoid CPU reloads during
RDF state transitions. Furthermore, if a CPU failure does occur during a state transition,
carefully review the EMS event log for signs of incorrect behavior. If the failure
occurred while RDF or the updating facility was stopping, check the Process Pair
Directory (PPD) to ensure that the appropriate RDF processes all have stopped; if they
have not, you must stop them manually.
If a state transition failure occurs during execution of a STOP RDF command and the
operation appears to be stalled, manually stop all of the RDF processes by issuing the
following command on both the primary and backup system:
STATUS *, PROG $SYSTEM.RDF.*, STOP
If a state transition failure occurs during execution of a STOP UPDATE command and
the operation appears to be stalled, manually stop all of the RDF updaters by issuing the
following command on the backup system:
STATUS *, PROG $SYSTEM.RDF.RDFUPDO, STOP
TMF Audited Volume Crash
RDF can recover from a crash of a TMF audited volume on the primary system. If the
volume is successfully recovered by volume recovery, then you do not have to perform
any special RDF procedures.
Caution. Issuing this command in this situation is only safe, however, if this is the backup
system for a single RDF environment.