Sorry for the verbose description but this is a curly one…
I have a project that includes a number of “Stored Procedure” Groups (11x at the moment) which all call the same SP in the database and Pass in 6 parameters (all tags) and writes back 4 bit tag values. These procedures are triggering every 2 sec & on average take 0.050 sec to complete.
The PLC is a ControlLogix 5500 series connected via IgnitionOPCUA using the “Allen-Bradley” driver suite via ethernet.
The Ignition version is 7.1.5 (b5670) and is running on a blade system with a dedicated SQL2005 instance on a separate blade to the ignition gateway system.
The problem I have is that very randomly (maybe one time in a couple of days or more) where a group will “error out” when trying to write the result bits to the PLC tags, or at least that is what the Events log indicates. When it happens all 4 bit tags have the same result code (which is Bad_NoDataAvailable) but Ironically the “Count” field displays a count of zero. at the same timestamp there is an info message saying “Group state changed to ‘errored’” also with a zero count. In each case there is another event 8-9 sec later indicating the group state set back to ‘running’ but this time with a count of 1.
All of the Groups tags exist in the SAME PLC yet the “problem” only appears to affect one group at a time - without any descernable pattern.
The four written Bits are crucial for returning important status information back to the PLC and the failure to write causes some grief at the PLC end when it doesn’t see the tags change. (Two of those tags form part of a “Handshake” between the PLC & Ignition)
I have tried changing between the tags being “Subscription” and “Read” to no avail.
I really want to understand what is causing this error & fix it if possible rather than putting a “band aid” fix into the PLC program. (Especially as it isn’t me that deals with the PLC code).