RDF System Management Manual

Introducing RDF
HP NonStop RDF System Management Manual—524388-003
1-6
Tips for Executing Fast Business Takeover
Operations
Tips for Executing Fast Business Takeover Operations
Take online dumps of your backup database as frequently as you take them on your
primary system. In this way, when you need to takeover on your backup system, you
will already have dumps available. Remember, if the RDF UPDATEROPEN attribute
is set to PROTECTED, you must stop the updaters and set it to SHARED before taking
online dumps of your backup database.
If your database is NonStop SQL/MP or NonStop SQL/MX and your applications form
the typical requestor-server environment where the requestors send requests into your
primary system from other locations, then you could start your servers on your primary
and backup systems. You must take care that you only route requestor work to your
primary system. This leaves your servers running essentially in standby mode on your
backup system.
RDF includes a trigger mechanism whereby user-supplied script can be executed
when you issue a TAKEOVER command on the backup system. The script is
completely user-configurable.
You configure a takeover trigger by issuing several SET TRIGGER commands followed
by an ADD TRIGGER TAKEOVER command. Among other things, the SET TRIGGER
commands identify a program-file and an infile.
program-file specifies the name of a Guardian object file be executed when a takeover
operation completes. That could be, for example, $SYSTEM.SYSTEM.TACL or
$SYSTEM.RDF.RDFCOM if you want to execute a TACL macro or RDF commands.
infile specifies the name of an edit file that will be passed to the trigger process when
that process is created. If program-file specifies $SYSTEM.SYSTEM.TACL or
$SYSTEM.RDF.RDFCOM, for example, infile would contain a TACL macro or RDF
commands.
This trigger mechanism is the preferred method of performing an RDF takeover and
resuming business activities on your backup system in the shortest time.
The following discussion provides alternative methods for business takeover
operations. These methods may not work for everyone, but you should consider them
to see if they might work for you.
When you lose your primary system because of some unplanned outage, you initiate
an RDF takeover operation. This brings your backup database into a consistent state,
typically within a small number of seconds.
You need to write a program that controls routing requestor work. This program can
monitor one of two mechanisms that report a successful RDF takeover:
•
RDF Event 724 reports the successful completion of an RDF takeover for the RDF
Control Subvolume named in the event.
•
RDFTKOVR file in the RDF Control Subvolume on your backup system. This file is
normally empty (eof = 0). Upon the successful completion of an RDF Takeover
operation, however, the key word "DONE" is written to the file.