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

Network Transactions
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
13-11
Takeover and the RETAINCOUNT Value
Takeover and the RETAINCOUNT Value
In order for all systems in an RDF network to execute phase 2 takeover processing
correctly, you must ensure that all image data potentially needed for undo is available on
each system. The way to achieve that is to set the purger’s RETAINCOUNT to an
acceptable value on each system. For a complete discussion about this attribute and how
it works, refer to Section 10, Triple Contingency
. (The same RETAINCOUNT
guidelines that apply to a triple contingency environment also apply to an RDF network
environment.)
Note that if you have not set the RETAINCOUNT properly and image files have been
purged that are subsequently needed for phase 2 takeover processing, the takeover
operations on the systems where the image data is missing might fail. In such a case,
your entire distributed database across all RDF backup systems could be compromised
with inconsistent data.
Network Validation and Considerations
A set of rules has been devised to ensure that all RDF subsystems in your configured
RDF network are consistent with each other.
1. You must validate all non network master subsystems before validating the network
master’s subsystem.
2. Because you cannot validate the network master until all non network master
subsystems have been validated, you cannot start the network master until all non
network master subsystems have been validated.
3. If you have validated a non network master, you are allowed to start that subsystem
even though the network master has not been validated.
See Appendix C for the error messages that can occur during validation steps.
RDF Re-Initialization in a Network Environment
For any number of reasons you may choose to stop some of your RDF network
subsystems and reinitialize them. This can be done without impacting the other
subsystems in the RDF network. When you reconfigure those subsystems after
initialization, there are several considerations.
Network Master Subsystem Initialization
When you reconfigure the subsystem, the network record must list all the non network
master systems and the information for each system in the network record must be
identical to the previous configuration. If not, validation will fail and you will not be
able to start the subsystem.
Note. It is strongly recommended that you validate the configurations of all RDF subsystems in
your RDF network with the RDFCOM VALIDATE CONFIGURATION command before you
attempt to start any. This would then guarantee that your entire RDF network is configured
correctly before you start any of the individual RDF subsystems.