RDF System Management Manual for H-Series RVUs (RDF 1.8)
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 335)), 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
7. T13 (network transaction started on \B)
8. T13 commit
9. T14 (non-network transaction)
10. T15 (network transaction started on \A)
11. T14 commit
12. T15 commit
At approximately the same time system \B executes:
1. T10 (network transaction started on \A)
2. T20 (non-network transaction)
3. T12 (network transaction started on \A)
4. T13 (network transaction started on \B)
5. T21 (non-network transaction)
6. T22 (non-network transaction)
7. T36 (network transaction started on \C)
8. T21 commit
9. T22 commit
10. T36 commit
11. T20 commit
12. T10 commit
13. T13 commit
14. T12 commit
RDF Takeovers Within a Network Environment 281