RSView Online Tag Changes

Hi,

I have RSView studio v4.0 running on one virtual machine, and RSLogix 5000 set up and running on another virtual machine. These are tied to a 1756-L63 controller. All communications are working well. I've noticed that if I try to change a tag name in the PLC while RSView studio is running, and referencing that same tag, in "test mode" I will get an error that the "tag is being read by one or more clients."

When I take the RSView station out of "test mode" I can change the PLC tag name.

When I put the RSView station back into "test mode" it can still read/access/modify the renamed tag, but I don't need to modify the tag reference in RSVIew. Why is that? It seems like RSView should flag an error that the tag reference is no longer valid.

Thanks

An answer derived from OMB processes

You're probably seeing an anomaly with RSLinx Enterprise involving the way it optimizes communications with ControlLogix.

Every Tag in a ControlLogix tag database has a 4-byte identifier. RSLinx Classic and RSLinx Enterprise have the ability to build up optimized blocks of tags using a process that involves querying the controller for a list of tagname and identifiers, then building up an optimized block of data based on the identifiers.

What's probably going on is that the optimized communication block mechanism still knows about the old Tag Name. So when RSView SE asks RSLinx Enterprise for "TagNameOld", it is able to just pull the correct offset from the optimized block.

You're hitting some sort of anomaly in the synchronization of the list of tag names that are on-scan and therefore locked from being changed, versus the actual list of tag names and identifiers that participate in an optimized data block.

It's also possible there's a multi-level Alias thing going on, where all the aliases resolve down to the base tag so it doesn't matter if you change the source tag.

My guess is that you're only getting comms to the "old" tag name by coincidence, and that it will fail after the system goes through a reboot or reconnection.