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

Lockstep Operation
HP NonStop RDF/IMP and IMPX System Management Manual—524388-001
14-5
Multiple Concurrent Lockstep Operations
The RDF lockstep protocol supports virtual disks, so you can store your database on
virtual disks managed by the Storage Management Facility (SMF). The RDF
LOCKSTEPVOL, however, must be a physical disk, and it must be configured to the
Master Audit Trail (MAT). Because the RDF lockstep file on the LOCKSTEPVOL is a
direct (physical, not logical) file, it can reside easily on a small portion of a physical disk
to store the file, and you can then subdivide the rest of the disk into virtual disks.
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 Configuring and Managing Generic
Processes in the SCF Reference Manual. For some attributes, however, restrictions
apply when the attributes are used with a lockstep gateway process.