RDF System Management Manual

Triple Contingency
HP NonStop RDF System Management Manual—524388-003
10-7
COPYAUDIT Restartability
COPYAUDIT Restartability
The COPYAUDIT command is restartable.
If an error condition aborts execution of a COPYAUDIT command, you merely correct
the condition and then reissue the command. Upon restart, RDFCOM quickly checks
the local system image files it had previously created to be sure they are still correct,
deletes the file it was working on at the time of the error condition, and then resumes
copying. Because it keeps track of where it was in the COPYAUDIT operation,
RDFCOM does not have to recopy the previously copied image files.
RDFCOM abends if it encounters network problems while searching the remote image
trails for missing audit information. If that happens, RDFCOM logs a message to the
EMS event log, but not to the home terminal.
If RDFCOM encounters network problems during any other phase of COPYAUDIT
execution, it does not abend. Instead, it logs a message to the home terminal and
aborts the COPYAUDIT command.
Using ZLT to Achieve Triple Contingency
Protection for Auxiliary Audit Trails
The COPYAUDIT command does not support auxiliary audit trails.
With the RDF/ZLT product, however, you can achieve the same protection without
using a COPYAUDIT command, and thereby protect RDF environments that include
auxiliary audit trails.
Triple Contingency Without ZLT
The triple contingency feature builds upon the ability to replicate to multiple backup
systems. With this feature you establish two essentially identical RDF configurations,
as follows:
RDF Subsystem #1
\A ---------> \B
RDF Subsystem #2
\A ---------> \C
Because the two subsystems run independently of one another, if system \A fails and
you execute TAKEOVER commands on systems \B and \C, the two backup databases
might not be synchronized with one another. The extractor for the \A-to-\B subsystem,
for example, might have replicated audit data to system \B, but, before the extractor for
the \A-to-\C subsystem could replicate the same data to system \C, system \A failed.
To correct this situation, you issue a COPYAUDIT command to transfer the extra audit
data from system \B to system \C. You then reissue the TAKEOVER command on
system \C, and the two backup databases are logically identical. At this point you can