CHAPTER 4: CREATING A STRATEGY WITH CONTROLLER REDUNDANCY
SNAP PAC Redundancy Option User’s Guide
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The completed dialog box will look something like this:
7.
For Controller Port, Software Retries, and Software Timeout, use the default settings:
Controller Port: 22001
Software Retries: 0
Software Timeout: 5000 msec
8.
Click OK.
9.
In the Select Control Engine dialog box, make sure the correct control engine is highlighted,
and then click OK.
10.
Click OK again to close the Configure Control Engines dialog box.
Step 3. Configuring Persistent/Redundant Data
Redundant variables (labeled as Persistent/Redundant in PAC Control) are persistent variables that
are replicated to an available backup controller whenever synchronization occurs. For optimal
performance of your redundant system,
best practice is to always use
Also, keep
in mind to use redundant variables only as necessary. Because each additional redundant variable
must be synchronized, too many can increase system overhead and slow down the system.
All redundant variables (as well as I/O changes) are synchronized no matter where the change is
initiated, either in a running chart or when using Debug Mode in PAC Control. I/O changes include
setting outputs, starting pulsing, and so on.
When a redundant variable that resides in a transactional chart is changed, the value on that
controller changes immediately, but it is not synchronized until the next sync block is encountered.
When a redundant variable resides in a
non
-transactional chart (a chart without sync blocks), the
