RDF/IMP, IMPX, and ZLT System Management Manual

Network Transactions
HP NonStop RDF/IMP, IMPX, and ZLT System Management Manual—524388-002
13-10
The Effects of Undoing Network Transactions
6. T
12
commit
7. T
13
(network transaction started on \B)
8. T
13
commit
9. T
14
(non-network transaction)
10. T
15
(network transaction started on \A)
11. T
14
commit
12. T
15
commit
At approximately the same time system \B executes the following:
1. T
10
(network transaction started on \A)
2. T
20
(non-network transaction)
3. T
12
(network transaction started on \A)
4. T
13
(network transaction started on \B)
5. T
21
(non-network transaction)
6. T
22
(non-network transaction)
7. T
36
(network transaction started on \C)
8. T
21
commit
9. T
22
commit
10. T
36
commit
11. T
20
commit
12. T
10
commit
13. T
13
commit
14. T
12
commit
Assume that the primary system \B goes down after having transmitted the commit
record for T
13
to its backup system \Y. At that point \Y has the commits for T
10,
T
13,
T
20
, T
21
, T
22
and T
36
. \Y only has to perform local undo (during which T
12
is undone).
The purger on \X (the network master) determines that the first transaction requiring
network undo is T
12
because that transaction was active on both \A and \B when \B
went down. Therefore, even though T
12
originated on \A and was committed on \A, it
must be undone on \X (the backup system of \A) because it was undone on \Y (the
backup system of \B). This ensures database consistency across both nodes. Note
that when the purger identifies the first network transaction that must be undone during
network undo processing, it logs an RDF 877 event message specifying that
transaction.