RDF/IMP, IMPX, and ZLT System Management Manual

Zero Lost Transactions (ZLT)
HP NonStop RDF/IMP, IMPX, and ZLT System Management Manual—524388-002
16-3
How It Works
Figure 16-3. ZLT Configuration With Standby and Backup Systems Located at
Separate Sites
If the standby and backup systems are not one and the same, you must remember to
set up remote passwords between the standby and backup systems. You must do so
with the same userid that has control over starting and stopping RDF.
If you lose your primary system due to an unplanned outage, you connect the remote
mirrors to the standby system, and then initiate a takeover operation on the backup
system. Before performing the takeover, RDF reads the remaining audit records from
the remote mirrors, and processes those audit records. Thus, RDF can read absolutely
all of the audit records that were generated on the primary system prior to the system
failure, and no committed data is lost.
Note. You must connect the remote mirrors to the standby system before starting the RDF
takeover operation; otherwise, the takeover aborts because RDF cannot find the disks you
configured in RDF for remote mirroring. In such a case, you should connect the disks and then
restart the RDF takeover operation.
System A
(RDF primary)
System B
(RDF backup)
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RDF traffic
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System C
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Audit-Trail
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Audit-Trail
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technology