RDF System Management Manual for J-series and H-series RVUs (RDF 1.10)

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 “RDF
System Files” (page 343) .
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 260).
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. One
48 Introducing RDF