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

Lockstep Operation
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
14-5
Multiple Concurrent Lockstep Operations
Multiple Concurrent Lockstep Operations
Because DoLockstep suspends the calling application until the associated lockstep
transaction commits on the backup system, a single application process cannot have
more than one lockstep operation in progress at any one time.
Multiple application processes, however, can invoke DoLockstep concurrently.
If called while idle, the RDF gateway immediately initiates a lockstep transaction to
perform the requested lockstep operation (one calling process, one lockstep transaction).
If called while it has a lockstep transaction active, the RDF gateway merely queues the
request. When the current lockstep transaction commits, the gateway initiates a new one
that performs the lockstep operation collectively for all of the queued requests (multiple
calling processes, one lockstep transaction).
Because the business transactions of each application process must have committed on
the primary system before the process called DoLockstep, the audit data for those is
guaranteed to be in the Master Audit Trail (MAT) when the lockstep transaction begins.
Thus, when the lockstep audit data is committed on the backup system, all audit data
generated in the MAT prior to that data is also guaranteed to be committed on the
backup system.
The Lockstep Gateway Process
The RDF lockstep gateway process is managed by the Subsystem Control Facility
(SCF). To start a lockstep gateway process, you must create and execute an SCF script
file. The recommended script settings are:
ASSUME PROCESS $ZZKRN
ADD #LSGO, &
NAME $ZLSGW, &
CPU FIRSTOF (1,2,3), &
PROGRAM volume.subvolume.LSGO, &
STARTMODE APPLICATION, &
STARTUPMSG "ENABLE <extractor-process-name>", &
AUTORESTART 10
START #LSGO
For detailed information about these attributes, see the SCF Reference Manual. For some
attributes, however, restrictions apply when the attributes are used with a lockstep
gateway process.
NAME
This attribute must be $ZLSGW. If you specify anything else, the lockstep gateway
stops and you cannot perform lockstep operations. Note that this means you can only
have a single lockstep gateway process running on your primary system.