RDF System Management Manual for J-series and H-series RVUs (RDF 1.10)

operation on the primary system. If, however, “kept-commits” have been encountered during phase
2 processing, a File Recovery position is not available; this is reported in RDF event 858. This last
situation will never occur in an RDF/ZLT environment because a File Recovery position is always
available with RDF/ZLT.
If an RDF event 888 is reported, then the specified File Recovery position is based on both phase
1 and phase 3 processing. Each system logs its own File Recovery position. While that position
can differ from one backup system to the next, the logged position for any single system is correct.
If you supply the returned File Recovery position to the TMF file recovery process on the primary
system, the process recovers the files on the primary database up to that point. If you use File
Recovery to a MAT position on all primary systems in the RDF network, in each case using the
returned File Recovery positions, then your primary distributed database will be consistent across
the RDF network.
You would use the File Recovery position with File Recovery in several situations: Assume you have
had an outage of your primary system, you have executed the RDF takeover operation on your
backup system, and you have resumed business transactions on your backup system. Assume
further that the former primary system has been repaired, it is back online, and you want to switch
your business transactions from the active backup database back to the former primary database.
To do so, you merely execute a planned RDF switchover from the backup to the newly restored
primary.
The problem with doing a planned switchover from backup to primary after an RDF takeover
operation is that some transactions might have committed on the primary system immediately prior
to the unplanned outage, and the outage brought down the extractor before it could send that
data to the backup system. In such a case, when you bring the primary system back up the two
databases are no longer synchronized because the primary database contains committed
transactions that are not in the backup database. Such transactions cannot be recovered.
In the past you would have had to synchronize your entire primary and backup databases. That
could be a lengthy task. Now you can simply use TMF file recovery to a MAT position. If you
execute this operation on your primary system using the MAT position specified in the RDF event
888 message (see the description of message 888 in Appendix C (page 346)), it brings the primary
database into the exact same state that the backup database was in upon completion of the RDF
takeover. Thus, after file recovery has completed, you can execute a normal planned switchover
from backup to primary.
NOTE: Due to the order transactions that commit on individual systems, file recovery might not
always be possible. If an 888 message is generated, however, it can be trusted.
The Effects of Undoing Network Transactions
Except with RDF/ZLT, phase 3 undo processing within an RDF network environment usually results
in other transactions being undone on every system in the network because the RDF product is
designed to make the safest, and most conservative, assumptions regarding all possible
interrelationships between transactions. This is best illustrated by example.
Consider an RDF network consisting of two RDF subsystem configurations (primary system \A
protected by backup system \X, and primary system \B protected by backup system \Y). Assume
that network transactions originate on both \A and \B, and that they update data on both \A and
\B. Assume further that each system also executes local, non-network, transactions.
More specifically, assume that system \A (the network master) executes:
1. T10 (network transaction started on \A)
2. T11 (non-network transaction)
3. T11 commit
4. T10 commit
5. T12 (network transaction started on \A)
6. T12 commit
284 Network Transactions