RDF/IMP, IMPX, and ZLT System Management Manual

HP NonStop RDF/IMP, IMPX, and ZLT System Management Manual—524388-002
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13 Network Transactions
The RDF/IMPX and ZLT products are able to guarantee backup database consistency
for transactions that update data residing on more than one RDF primary system.
RDF/IMPX and ZLT can map the volumes being protected to both the MAT and
auxiliary audit trails.
Without planning for network transaction support, the RDF product cannot guarantee
database consistency among the associated backup systems following the failure of
one of the primary systems.
Support for network transactions requires two major external changes.
1. If you have a distributed database spread over several RDF primary systems, you
must configure an RDF network wherein each primary system residing on its own,
mutually exclusive node has its own RDF subsystem that replicates its local data to
its own backup system. This is referred to as an RDF network because each RDF
subsystem knows the names of the systems protected by all other RDF
subsystems in the network. One, and only one, RDF subsystem within the network
must be configured as the network master.
2. If you lose one or more RDF primary systems in the RDF network, you must
execute RDF takeover operations on all backup systems in the network.
For those primary systems still alive, you must first quiesce all application activity
(both local and remote) so that no further database updates are being performed,
and then bring down the communication lines between the primary and backup
systems before initiating the takeover.
With network transaction support, you must now be more careful when creating
Enscribe files that have alternate key files. Specifically, when you create an Enscribe
file with an altkey file you must ensure that both files reside on the same primary
system and that both are protected by the same RDF subsystem. If you do not do so,
then the updater responsible for creating the file on the backup system will not create
the file; rather, it will report an error 740 when it determines that the altkey file is not
protected by its RDF subsystem.
Note. Network transaction processing is currently not supported in configurations that use the
triple contingency feature. You must use RDF/IMPX or ZLT to protect all databases open to
network transactions.