Why Use Kepware Static Tags Rather Than FTView SE HMI Tags ?

[PL_9524549]

Hi,

I have used Kepware with Siemens WinCC SCADA in the past to communicate with Rockwell Control Logix PLC's but did not create any static tags within Kepware.  I created a tag database within WinCC and the WinCC SCADA tag addresses contain the path to the OPC topic and the controller tag within the PLC.  I am now looking at an existing FTView SE application that is using Kepware to communicate with Mitsubishi PLC's but has created static tags within the Kepware configuration so the FTView application uses the Kepware static tags directly without having to create HMI tags in the FTView application.

Are there any performance advantages by creating static tags in Kepware and using them directly within the FTView  application as opposed to creating the tags within the FTView system ?  How does the Kepware comms driver handle comms in these two situation ?  

[pshashipreetham · Accepted solution]

Hi, 

When you create static tags directly in Kepware, you’re essentially letting Kepware handle the tag resolution and polling cycle internally. That can give a few practical benefits compared to relying only on dynamic tags from FactoryTalk View SE (FTView):

• Lower overhead on the HMI side – FTView doesn’t need to build and maintain its own separate tag list or constantly resolve OPC paths at runtime. It just subscribes to known Kepware tags.

• Centralized tag definitions – All your PLC addresses live in one place (Kepware). If a PLC address changes, you update it once in Kepware, and all-consuming clients (FTView, historians, scripts, etc.) will automatically see the change.

• More efficient communications – Kepware optimizes reads/writes when it knows the complete set of tags in advance. With dynamic HMI tags, it can’t batch as effectively because the subscriptions are more ad-hoc.

• Cleaner diagnostics – It’s easier to troubleshoot data quality and comms in Kepware’s diagnostics when you know precisely what tags it is serving.

That said, this doesn’t mean static tags are strictly faster; it depends on the number of tags you have and how frequently they are updated. If you only have a small set of HMI tags and don’t expect them to change, creating them directly in FTView is fine. However, for larger systems or when multiple clients will consume the same data, static Kepware tags provide better consistency and reduced administrative effort in the long run.

In short:

• Few tags, simple system: FTView HMI tags are fine.

• Lots of tags or shared data: Use static tags in Kepware.

Thanks,

[PL_9524549]

Hi,

Thanks for your reply. 

Creating tags in Kepware might be ok when using a Rockwell FTView SCADA as you then don't need to create HMI tags within the FTView application. However when using an application like WinCC you would end up having to create two tag databases: one in Kepware and one in WinCC.  I have used Kepware with WinCC and Rockwell ControlLogix PLC's but created the tags in WinCC and not in Kepware.  I'm would be interested to know if others create two sets of tag databases when using SCADA applications which require a tag database .