Applies To:
  • CitectSCADA x.x
Summary:
Citect Device Drivers have standard parameters for changing their operating characteristics. What does the parameter 'Retry' mean? 

Solution:
First, it should be noted that drivers have default values for these parameters. During development the best combination of default values for these values is setup based on our results from testing and our experience with all drivers. We advise that the standard parameter entries are not altered from their defaults unless otherwise advised by Citect support.

The parameter 'Retry' is the number of times to retry a request which has timed out after no response. A protocol should only require 1 retry. The occurrence of retries in normal operation should be extremely rare. If more retries are required this indicates a serious communications problem which should be fixed. Relying on retries to cover up an underlying communication problem is bad practice.

If the number of retries is set high then this will increase the time taken to trigger a redundancy swap overs.

Some protocols, particularly those based on networks provide their own retries. In this case the driver need not support retries.

 
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