Rdf Control Subvolume; Other Rdf Features; Triple Contingency; Loopback Configuration (Single System) - HP NonStop RDF J-series RVUs Management Manual

In the preceding examples, each RDF configuration operates entirely independently of the other
RDF configuration primaried on the same node; that is, each RDF system has its own extractor
and monitor process. In this way, Expand problems affecting one configuration might not
necessarily affect the others (depending on the configuration).

RDF Control Subvolume

The INITIALIZE RDF command includes a control subvolume suffix parameter (SUFFIX char),
where char is an alphanumeric character. If you include this parameter, the RDF control
subvolume on $SYSTEM will be the local (primary) system name without the backslash and with
the specified character appended to it. If you omit this parameter, the RDF control subvolume
on $SYSTEM will merely be the local system name without the backslash.
If you want to have several RDF susbsystems configured on the same primary node, the RDF
configuration for each RDF subsystem must have its own control subvolume and you must
specify the SUFFIX parameter when you initialize each subsystem. For example, if the name of
your primary node is \BOSTON, you could specify "1" as the SUFFIX when you configure the
first RDF subsystem, and its control subvolume will be BOSTON1. If you specify "2" as the SUFFIX
for your second RDF subsystem, then its control subvolume is BOSTON2. Both are located on
$SYSTEM, but each RDF subsystem has its own control subvolume.
For a description of the files in the control subvolumes on the primary backup systems, see
System Files" (page 362)

Other RDF Features

Triple Contingency

If you are replicating your database to two backup systems and then lose your primary system,
you can perform an RDF takeover on both the backup systems upon loss of the primary system
and continue application processing on the new system within minutes. To proceed with full
RDF protection, however, you must:
1. Initiate a takeover on two of the backup systems.
2. Synchronize the two databases.
3. Configure the two systems as a primary-backup pair.
4. Initialize and start RDF on the system that you want to be the new primary system.
Depending upon the size of your database, the second step listed, database synchronization,
could take days to accomplish without the RDF triple contingency feature. Triple contingency,
however, streamlines this step, enabling you to achieve rapid database synchronization after a
takeover operation. Triple contingency allows your applications to resume, with full RDF
protection, within minutes after the loss of your primary system, provided that the two systems
are not too far behind.
The triple contingency feature builds upon the ability to replicate to multiple backup systems.
To use this feature, you establish two essentially identical RDF configurations:
RDF Configuration #1
\A ---------> \B
RDF Configuration #2
\A ---------> \C
To achieve Triple Contingency protection, see the various requirements that are outlined in detail
in Chapter 10 (page

Loopback Configuration (Single System)

A loopback configuration is one where the primary and backup systems are the same system.
This configuration is of no use in a disaster protection plan, but can be useful for testing purposes.
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271).
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Other RDF Features 53