Performance when using PCO to write OPC tags

[former_member859939]

Hi,

We are using SAP PCO to write tags from SAP MII to FSGateWay OPC.

These 3 applications are on 3 seperate  servers in the network.

When we dispatch the data to OPC we need to write 1000 ~ 1200 tags. All the tags are written in about 4 PCo Queries. The problem is that performance is very slow. In the logs of the Agent Instance I see that every tag is written seperatly to the OPCserver. Even though the PCO query writes multiple tags at once.

It is taking about 120ms per tag. Which sounds normal if  you think of all the actions involved. However this adds up to about 2 minutes before all the data is dispatched and this is not acceptable.

I'm looking for any ways to improve the performance of the tag writing. Is it possible to have PCO write multiple tags at once to the OPC server or will it always be seperate?

We are using SAP MII 15.0 SP4 Patch 5 and SAP PCo 15.0.5.2522.

Thanks,

Philippe

[former_member196557]

Hi Philippe,

First, if you have the PCo Agent Instance in Verbose log mode, do you see a log message that states

MassStore Tag Query Received for xxx items

where xxx is the number of tags configured in the PCoQuery action.

If you do not find this log message, the Mass Store support is not available in these versions and you will need to Patch MII to the latest SP and Patch for MII (I have tested with SP07 Patch 4).  and PCo 15.0 SP06 Patch 6.  You can also upgrade PCo to 15.1 latest SP and Patch; it is backwards compatible with MII 15.0 ( I tested the a multiple tag write with MII 15.0 SP07 Patch 6 and PCo 15.1 SP02 Patch 3 and it is successful). 

If you do find this message, then MII/PCo are attempting to ask the OPC Server to write multiple tags to the PLC.

Note that when you write tags or read tags from MII though PCO for the first time, PCo has to retrieve the actual tag address from the OPC along with the meta-data and persist it in the internal PCo Query buffer, so initial query takes longer than the subsequent queries for the same tags.

Regards, Steve

[former_member859939]

Hi  Steve,

Thanks for your quick response.

I do see the message 'MassStore Tag Query Received' in the logs. However, this is always for '1' item'. This does not seem right then?

In my PCO Query I do not specify the tags, they are passed dynamically to the query through the links 'SelectedTags' and 'SelectedTagsValue'.

Also I am using tagValueEncoding with base64encode because some description contain comma's which are otherwise viewed as seperators.

[former_member196557]

Hi Philipe,

In the logs there should be an Information message similar this:

Tag Query:  STORE 'SIM&#x2f,SIM&#x2f,Float1' = '1.1','SIM&#x2f,SIM&#x2f,Float2' = '1.2','SIM&#x2f,SIM&#x2f,Float3' = '1.3',;

where each separate 'tagname'='value' are separated by commas. If you are passing a number of stags in this message you may not be able to see the entire message in the log.

If you message looks like this:

Tag Query:  STORE 'SIM&#x2f,SIM&#x2f,Float1' = '1.1',;

and there is a STORE command message per tag, then MII instance needs to be patched to the latest SP and Patch.

Regards, Steve

[former_member859939]

Hi Steve,

Thanks again!

It looks like we will need to do the patch because this is indeed the case.

I will test again when it is done.