# Block Transaction Group with OPC Data

**URL:** <https://forum.inductiveautomation.com/t/block-transaction-group-with-opc-data/6894>\
**Category:** Ignition\
**Created:** [July 19, 2013, 5:43am UTC](https://forum.inductiveautomation.com/t/block-transaction-group-with-opc-data/6894 "2013-07-19T05:43:19Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![allenr8](https://avatars.discourse-cdn.com/v4/letter/a/e56c9b/32.png) [@allenr8](https://forum.inductiveautomation.com/u/allenr8)\
**Post date:** [July 19, 2013, 5:43am UTC](https://forum.inductiveautomation.com/t/block-transaction-group-with-opc-data/6894/1 "2013-07-19T05:43:19Z")

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If I am using a Block Transaction group to much a large chunk of OPC data - at what rate is the OPC data polled?

I know if I use SQLTags and they are leased they are polled at the fast rate once part of the transaction group.

Since you don’t really specify a scan class for the OPC items I’m not quite sure how fast they will scan - does anyone know this?

I am trying to keep it fairly slow since it just for recipes and over radio comms.

Thanks

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**Author:** ![Robert.McKenzie](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/robert.mckenzie/32/4134_2.png) [@Robert.McKenzie](https://forum.inductiveautomation.com/u/Robert.McKenzie)\
**Post date:** [November 23, 2013, 12:58am UTC](https://forum.inductiveautomation.com/t/block-transaction-group-with-opc-data/6894/2 "2013-11-23T00:58:17Z")

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The OPC items in a Transaction Group always run at whatever the Execution Scheduling rate is. The only time this isn’t true is if you use the ‘Override OPC subscription rate’ in the Options tab.