Deleting Unused Tags with assigned Alias from RSlogix 5000

remullis

Member
Join Date
Oct 2012
Location
Georgia
Posts
179
I am currently working on a project where IO is not being used but previously was used in the field. In logix for example I have a tag where we have no wires landed it does still reference the slot and channel. This particular tag was only used in a function block routine for alarming. I deleted this routine from the main and the FBD routine because the tag would not delete due to actively being used in a program. When I try to delete this specific tag in "Edit" mode it gives me the following error: Failed to delete object. Can't delete in its current mode/state. But it no longer exist? I have quite a bit of tags not being used but assigned in the particular IO rack and would like to clean it up. Any ideas?

I have had success in some instances where if the tag was actively used somewhere I would cross reference and if Its not used I would delete and this would allow me to delete the tag in the tag list.
 
Typically, if the tag was 'on scan' by another system you won't be able to delete it. If an HMI/SCADA package was reading the tag you wish to delete, the tag reference still exists in the communications library and because of this it won't let you delete it.

Sometimes, if you shutdown your HMI/SCADA system and any IO/OPC servers to stop all external communications the PLC you can then delete it. Once the IO servers startup again they will re-scan the controller for all available tags and rebuild itself w/o the reference.

I'm sure other reasons exist for this, unfortunately the best option is to shut things down, clean up your code, download and bring everything back up. Best way to get to a 'clean' slate.
 
You cannot delete a Module-Defined Tag, so if the module is in the I/O tree, leave its tags alone.

You cannot delete a tag that has an Alias tag assigned to it. If you delete the Alias first, you should be able to delete the base tag too.

In the case you describe where a tag was being used for Alarming, I agree that it's likely that it's unable to be deleted because it's part of an optimized packet that's on-scan by an HMI system.
 
Thanks guys, It is used in WW. So if I delete this out of wonderwares tag dictionary it probably would not allow me to delete these still until the IO server does a rescan after restart, correct?

This may be something I would need to do during a planned outage.

With that said I am able to create a new tag name and assign it the same alias/base tag but it just seems to be a mess at the end of the day.

Thanks
Rich
 
Hi

I often rename tags as unused_ 1 etc untill I get a chance to download
To the plc and this keeps them in line in the tags or sometimes I place a z in front so they are at the bottom.

Donnchadh
 

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