RDF System Management Manual for J-series and H-series RVUs (RDF 1.10)

If CommitHoldMode mode is activated, TMF stops all further commit operations. Because transactions
on the primary system cannot commit or abort while the remote mirror is unavailable, you achieve
ZLT protection if you should lose your primary system while commit-hold mode is activated. When
such an event occurs, however, transaction processing on the primary system effectively stops.
TMF provides another configuration attribute associated with CommitHoldMode:
COMMITHOLDTIMER. If CommitHoldMode is activated, the COMMITHOLDTIMER value specifies
how long you want CommitHoldMode to remain activated and what to do when that time is
reached. The parameters are:
COMMITHOLDTIMER {timeout [ON TIMEOUT {SUSPEND|CRASH}] | -1 }
If timeout is set to a positive value (from 5 seconds to 24 hours) and CommitHoldMode becomes
activated, all commit processing stops until either you correct the problem that caused activation
of COMMITHOLDMODE or the timeout value is reached. If the timeout value is reached, TMF
performs the action specified by the ON TIMEOUT option (SUSPEND or failure).
CommitHoldMode affects transaction processing on your primary system dramatically when a
remote mirror becomes unavailable. If a remote mirror becomes unavailable, you must choose
whether you want ZLT protection or the resumption of transaction processing.
If ZLT protection is critical to your disaster recovery plan, specify ON TIMEOUT CRASH. Crashing
TMF under these circumstances provides ZLT protection.
If it is important to resume transaction processing on the primary system, specify ON TIMEOUT
SUSPEND. Suspending commit-hold mode under these circumstances, however, deprives you of
ZLT protection should you lose the primary system to some unplanned outage.
If you set timeout to -1, TMF maintains an activated commit-hold state indefinitely until you correct
the issue causing the activation, you manually suspend commit-hold mode, or you turn off
commit-hold mode.
The default timeout value is 60 seconds and the default action upon reaching the timeout value is
SUSPEND (which means loss of ZLT protection).
Hardware Setup
To set up RDF for ZLT with remote mirror capability you must have established your hardware setup
first. That is, you must set up remote mirroring for every audit trail volume that relates to the RDF
environment before you configure RDF.
NOTE: Because the remote mirrors will be connected to your standby system in the event of an
unplanned takeover, you should choose disk names that will not conflict with disks already connected
to the standby system.
ZLT is currently only supported with an HP StorageWorks XP disk array.
Assigning CPUs on the Standby System
By default, the same CPUs configured for each extractor on the primary system are used for the
corresponding extractor on the standby system, provided that both the necessary primary and
backup CPUs are available on the standby system.
If the necessary primary or backup CPU for an extractor is not available on the standby system,
the RDF monitor process selects from those CPUs that are available. If the monitor must select the
primary CPU for all extractors, it puts the primary processes of the extractors in as many different
CPUs as possible to achieve load balancing provided there are enough CPUs. If, for example, you
have six extractors configured, but you only have two CPUs on your standby system, the monitor
places the primary processes of three extractors on one CPU and the primary processes for the
other three extractors on the other CPU. If the monitor process selects the primary CPU of an
extractor and the configured backup CPU is not available on the standby system, then the extractor
does not run as a process pair; it only has the primary process.
Hardware Setup 323