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

Lockstep Operation
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
14-3
DoLockStep Execution
Typically you should explicitly bind the object into your program. The object file
(LSLIBTO) is very small, and there are no benefits to treating it as a user library.
To bind LSLIBTO into your program, issue the following statement:
Select Search <$vol.subvol>.LSLIBTO
where <$vol.subvol> is the location where you have placed the object file.
If you do not want to bind the object into your program and if you do not already use a
user library, then you can skip the bind step and treat LSLIBTO as a user library.
The TAL procedure call syntax is:
status := DoLockstep
where status is an int.
DoLockStep Execution
DoLockstep communicates with a RDF gateway process that acts as the coordinator of
the lockstep operation. This gateway initiates a new lockstep transaction against a
special RDF lockstep file. The gateway passes information about the lockstep
transaction to the RDF extractor. When the RDF receiver has flushed all audit records
up to and including the lockstep audit into the image trail, it replies to the extractor that
the lockstep data is safe. When the extractor receives that information, it replies to the
gateway which, in turn, passes status back to the DoLockstep call, and the latter then
returns status to the application.
DoLockstep is a waited operation that waits until the RDF subsystem has safely stored
all audit data up to and including all audit data associated with the lockstep transaction
in the image trail. Therefore, if the communications line between the primary and
backup nodes should go down after the application has called DoLockstep, the
application will wait until the line comes back up and the lockstep audit data is safely
stored.
DoLockstep returns one of the following three states:
LockStepDone (value is 31428)
All audit data associated with the lockstep operation has been safely stored in the
image trail on the backup system.
LockStepDisabled (value is 31429)
Only returned when you have disabled lockstep processing. When this condition
code is returned to your application, what your application does next is up to you.
For example, you may choose to execute a recovery transaction that backs out the
work of the previous business transaction, or you may wish to continue as if the
Note. The DoLockstep procedure can only be invoked from TAL and COBOL85 programs.
Non-native C and native mode languages (C, C++, native mode COBOL, and pTAL) are not
supported.