RDF System Management Manual

Network Transactions
HP NonStop RDF System Management Manual—524388-003
13-8
Communication Failures During Phase 3 Takeover
Processing
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.
Takeover and File Recovery
When a takeover operation completes in an RDF network environment, the purger logs
two events: one reports a safe MAT position (indicating that all committed data up to
that location was successfully applied to the backup database), and the second (888 or
858) reports whether or not a File Recovery position is available for use on the primary
system. The RDF event 888 reports that a File Recovery is available and it includes
the exact sno and rba to be used for a File Recovery operation on the primary system.
If, however, “kept-commits” have been encountered during phase 2 processing, a File
Recovery position is not available; this is reported in RDF event 858. Note that this
last situation will never occur in an RDF/ZLT environment because, with RDF/ZLT, a
File Recovery position is always available.