RDF/IMP and IMPX System Management Manual (RDF 1.4+)

Lockstep Operation
HP NonStop RDF/IMP and IMPX System Management Manual—524388-001
14-7
Reenabling Lockstep
want to disable lockstep processing to allow your applications to resume their work
without lockstep operations.
When lockstep is disabled, remember that your original transaction has already
committed on the primary system. If you should subsequently lose the primary system
and do a takeover on the backup system, the transaction may or may not have been
committed in the backup database depending on whether or not the extractor got all of
the original audit data over to the backup system before the primary system failed.
Reenabling Lockstep
To reenable lockstep processing:
1. Change DISABLE to ENABLE in the STARTUPMSG attribute script.
2. Manually delete the RDF lockstep gateway process from SCF.
3. Run the changed SCF script.
When SCF restarts the gateway, lockstep processing is enabled.
Lockstep Performance Ramifications
By definition, a lockstep operation will increase the response time of your application
because, after having invoked DoLockstep, the application must wait for the data to
become safely stored in the backup system’s image trail. The extractor and receiver
processes have been streamlined to facilitate lockstep processing, but a short delay is
unavoidable.
Expand problems or CPU failures that trigger extractor and receiver restart operations
could also increase response times.
As described under Multiple Concurrent Lockstep Operations, the RDF gateway only
ever has a single lockstep transaction in progress at any one time. If called while a
lockstep transaction is in progress, the RDF gateway merely queues the request.
Consequently, if an application process issues a DoLockstep request immediately after
the gateway has started a lockstep transaction, that request must wait to be performed
until the current lockstep transaction is commited on the backup system. That could
also increase response times.
Lockstep and Auxiliary Audit Trails
You cannot use lockstep processing in an RDF subsystem that is protecting auxiliary
audit trails.