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

Triple Contingency
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
10-5
The COPYAUDIT Command
disk). Thus, as long as the RTD times of the extractors on the two backup systems are
less than 36 hours apart, the triple contingency protocol will work successfully.
Similarly, if you believe the two receiver processes will never be more than 48 hours
apart in their RDF processing and your image trail file sizes are such that approximately
20 rollovers occur every 24 hours, then you should set the RETAINCOUNT to 40 on
both backup systems.
You set the RETAINCOUNT parameter by issuing the following command:
SET PURGER RETAINCOUNT num
where num is a number within the range 2 through 5000. The default is 2.
You can alter the RETAINCOUNT only when RDF is stopped.
You alter the RETAINCOUNT parameter by issuing the following command:
ALTER PURGER RETAINCOUNT num
where num is once again within the range 2 through 5000. (Before entering this
command, however, you must first stop RDF.)
The COPYAUDIT Command
If the primary system fails, you must execute two takeovers: one on each backup system.
Upon successful completion of both takeovers (signalled by a 724 message in the EMS
event log of each backup system), the databases on the two backup systems will almost
assuredly not be identical: one of the systems will have been further ahead of the other
in its RDF processing when the failure occurred.
The COPYAUDIT command copies missing audit information from the backup system
that was further ahead in its RDF processing (had the most amount of audit data) to the
system that was further behind (had the least amount of audit data).
Upon successful completion of the two takeovers, examine the EMS event log on both
backup systems for a 735 message. That message, which follows the 724 message in the
log, specifies the last position in the MAT that was seen by the receiver process.
Compare the MAT positions in the two 735 messages and determine which of the two
systems was further behind in its RDF processing when the failure occurred (that is,
which system had received the least amount of audit data from the extractor by the time
the primary system was lost). Then issue a COPYAUDIT command on that system,
specifying the name of the other backup system and its RDF control subvolume.
The syntax of the COPYAUDIT command is as follows:
COPYAUDIT , REMOTESYS sys, REMOTECONTROLSUBVOL subvol
where sys is the name of the other system (the backup system that has the most
amount of audit information) and subvol is the name of the RDF control subvolume
on that system.