RDF/IMP, IMPX, and ZLT System Management Manual

Zero Lost Transactions (ZLT)

HP NonStop RDF/IMP, IMPX, and ZLT System Management Manual—524388-002

16-7

ZLT Takeover Operations

If ZLT is configured and enabled when a TAKEOVER command is issued on the

backup system, the overall takeover operation executes in two phases.

Phase 1 (ZLT Processing)

RDFCOM stops all RDF processes on the backup system. If the standby and backup

systems are not the same system, RDFCOM copies the RDF configuration file on the

backup system to the standby system. RDFCOM then starts an RDF monitor process

on the backup system. That monitor then starts the extractor(s) on the standby system

and the receiver(s), purger, and updater(s) on the backup system.

Each extractor logs an event (901) reporting it is started for ZLT processing, and sends

all remaining audit records to its receiver. When an extractor reaches the end of its

audit trail, it sends a “ZLT finished” indication to its receiver, and logs an event (900)

reporting it has completed its ZLT task. When all extractors are finished, they are

terminated and deleted. Upon receiving the “ZLT finished” indication, each receiver

logs an event (903) reporting it has completed its ZLT task, and tells its updater to

commence normal takeover operations. When all receivers have finished their ZLT

processing, the overall takeover operation proceeds to phase 2.

Phase 2 (Takeover Processing)

The initial part of Phase 2 takeover processing is performed by the purger in building

the undo lists. When an updater reaches the end-of-file of its image trail, it asks the

purger for an undo list. (The purger cannot start building the undo lists until all

receivers have finished their ZLT processing.) The updaters use those lists to back out

any audit for transactions that were unresolved on the primary system at the time of

the unplanned outage.

ZLT Events

Event Management System (EMS) events are logged to report the progress of the ZLT

operation in the various RDF processes. For descriptions of these messages, see

messages 900 through 903 in appendix C.

Note. Before issuing the TAKEOVER command, you must have connected the remote mirrors

to the standby system. When the remote mirrors are connected to the standby system, the

audit records on the remote mirrors have no relationship to the audit trail on the standby

system. The remote mirrors are not part of the TMF configuration of the standby system.