RDF/IMP, IMPX, and ZLT System Management Manual

HP NonStop RDF/IMP, IMPX, and ZLT System Management Manual—524388-002
14-1
14 Process-Lockstep Operation
The RDF/IMPX and ZLT products include the process-lockstep operation, which is
process-based. That is, when a process invokes the lockstep operation for a business
transaction, the process must wait until all audit records associated with that business
transaction are safely stored in image trails on the backup system before continuing.
A lockstep operation consists of the following steps.
1. A process starts a business transaction and does database updates.
2. The process calls endtransaction to commit the work.
3. The process issues a DoLockstep procedure call.
4. The DoLockstep procedure communicates with an RDF gateway process.
5. The gateway starts a lockstep transaction against an RDF lockstep file.
6. The gateway communicates with the RDF subsystem regarding the lockstep
transaction.
7. The RDF subsystem tells the gateway when lockstep audit has been safely stored
on the backup system.
8. The gateway returns status to the DoLockstep procedure.
9. DoLockstep returns status to the process.
Thus, although the business transaction is actually committed on the primary system
(and the file locks or table locks are released), the process cannot continue processing
until all of the audit data associated with that transaction is safely stored in the image
trails on the backup system).
While the process waits until DoLockstep completes, other processes can view and
modify the just-changed records, and this must be understood and taken into
consideration by the application designer.
The RDF/IMPX and ZLT independent product CDs include the following files
associated with the lockstep capability:
Note. The lockstep capability can be used only for replicating Master Audit Trail (MAT) data.
In addition, the lockstep capability cannot be used in an RDF network environment.
Furthermore, you can have only one RDF subsystem configured for lockstep on a given node
because the gateway can only be configured to a single extractor process.
SLOCKCOB Sample code for invoking the DoLockstep procedure from a
COBOL 85 program.
LSGO RDF lockstep gateway object code.
LSLIBTO DoLockstep procedure object code.
FDOLOCK Forward declarations of the DoLockstep procedure call.