HP NonStop RDF, Руководство по управлению

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TAKEOVER
The TAKEOVER command puts the backup database into a consistent state with regard to
transaction boundaries, after which it can become your new database of record.
TAKEOVER [!]
If you omit the ! option, then RDFCOM attempts to reach the primary system to verify that it is
indeed inaccessible. If it is able to reach the RDF monitor and extractor on the primary system,
then the TAKEOVER command is immediately aborted. If the primary system is inaccessible, it
then prompts you to confirm that you really want to execute the takeover. The reason for both
tasks is to allow you to be certain you are not mistakenly issuing the TAKEOVER command.
If you include the ! option, then the step to access the primary and the prompting are both omitted
and the takeover operation proceeds immediately.
NOTE:
If you include the ! option and the primary system is still accessible, then the TAKEOVER
command may very well put your backup database out of synchronization with the primary
database. Therefore you should only include the ! option if you are absolutely certain you want
to proceed unequivocally with the takeover operation.
Where Issued
Backup system only.
Security Restrictions
You can issue the TAKEOVER command if you are the member of the super-user group that
initialized RDF.
Usage Guidelines
The TAKEOVER command is customarily issued when the primary system fails or otherwise
becomes unavailable, and you want to make the backup database your new database of record
for your applications.
CAUTION:
The TAKEOVER command is not a normal operational command. Operators should
never issue this command strictly on their own initiative. Issue this command only when
specifically told to do so by someone in high authority.
For a thorough discussion of a variety of issues you need to plan for in order to facilitate a fast
overall takeover operation that moves your application processing to the backup system, see the
discussion for
“How to Plan for the Fastest Movement of Business Operations to Your Backup
System After Takeover” (page 144) in Chapter 5 . The TAKEOVER command normally takes only
a matter of a few seconds, but all the other considerations and tasks delay moving your
applications to the backup system. With advanced planning, RDF customers have been able to
recover from loss of the primary system and resume operations on the backup system within a
small number of minutes, but it requires advanced planning.
For takeover considerations in a ZLT environment, see Chapter 17 (page 337) .
If RDF is running with Update On in a non-ZLT environment, then RDFCOM sends a takeover
message to each RDF process on the backup system, and an RDF monitor is not started.
If RDF is running with updating off, RDFCOM stops the receiver and purger processes and starts
the monitor in takeover mode. The monitor then starts the receiver and purger processes and all
updater processes.
RDFCOM Commands 255