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

Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
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Lockstep Operation
Lockstep operation, which is available with the RDF/IMPX product, prevents an
application from executing further processing based on a committed business transaction
until all audit associated with that transaction is safely stored in the image trails on the
backup system.
A lockstep operation consists of the following steps.
1. An application starts a business transaction and does database updates.
2. The application calls
endtransaction to commit the work.
3. The application issues a new
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 application.
Thus, although the business transaction is actually committed on the primary system, the
application is not allowed to continue processing until DoLockstep returns status to the
application (that is, the application cannot execute further processing based on the
committed business transaction until all of the audit data associated with that transaction
is safely stored in the image trails on the backup system).
The RDF/IMPX independent product CD includes 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.
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.