RDF/IMP and IMPX System Management Manual (RDF 1.4+)

Network Transactions
HP NonStop RDF/IMP and IMPX System Management Manual—524388-001
13-7
Takeover Phase 3 Performance
Takeover Phase 3 Performance
The speed with which a takeover completes for an entire RDF network varies based on
the number of systems in the network and how far any system had fallen behind when
the takeover was initiated.
For example, if you have three systems in your RDF network, and all extractors on all
three systems were keeping up with audit generation on their systems, and then one
system fails, the takeover operations may only take a modest number of additional
seconds to complete phase 3 takeover processing.
In contrast, if you have three systems in your RDF network, and one extractor had
fallen 60 minutes behind at the time its system went down, then phase 3 takeover
processing on the other two systems will take many more seconds to complete. The
reason for this is that phase 3 processing on the two systems that were not behind will
have to go through 60 minutes of data to determine what must be undone due to data
missing on the system that had fallen behind.
A variation of the first example is that no extractors have fallen behind, but you have 25
systems in your RDF network. In such a case, phase 3 processing may take many
additional seconds because data must be checked for so many different systems in
order to determine what network data might be missing from the various systems in the
RDF network.
Communication Failures During Phase 3 Takeover Processing
If one RDF subsystem is unable to reach the backup system of another RDF subsytem
during phase 3 processing, phase 3 processing stalls until the communication line
comes back up. This can lengthen the overall duration of takeover operations on all
backup systems. Should this type of stall occur, the RDF subsystem issues an event
message alerting operators to the situation.
Takeover Delays and Purger Restarts
During phase 3 purger work, the network master needs information from the other
purger processes in the RDF network, and, during the latter part of phase 3
processing, the non-network master purgers need information from the purger of the
network master. When a purger process is waiting for information from another purger,
it waits for up to 60 seconds, during which time it does not respond to certain requests
(such as STATUS RDF). After a purger has waited 60 seconds, it quits the operation
and restarts. This allows the purger to read the $RECEIVE file, respond to messages
that have been waiting for replies, and then retry phase 3 processing.
Takeover Restartability
As has always been the case, the RDFCOM TAKEOVER command is restartable.
Therefore, if a takeover operation terminates prematurely for any reason on any
system in an RDF network, it can be restarted.