# Optimise data access on SIemens PLC

**URL:** <https://forum.inductiveautomation.com/t/optimise-data-access-on-siemens-plc/25237>\
**Category:** Ignition\
**Created:** [May 22, 2019, 5:38pm UTC](https://forum.inductiveautomation.com/t/optimise-data-access-on-siemens-plc/25237 "2019-05-22T17:38:45Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![SergioS](https://avatars.discourse-cdn.com/v4/letter/s/da6949/32.png) [@SergioS](https://forum.inductiveautomation.com/u/SergioS)\
**Post date:** [May 22, 2019, 5:38pm UTC](https://forum.inductiveautomation.com/t/optimise-data-access-on-siemens-plc/25237/1 "2019-05-22T17:38:45Z")

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Good morning at everybody,  
actually I’m reading data from different plc (n.9 S7-1500 and n.3 S7-300 ) dislocate on differents networks (and plants).

Total tags are 12000 tags .

All the tags are into the same scan class.  
Networks performances to reach each plc are differents depending of traffic and delais.

In this condition , Do you think that is better create a dedicate scan class for each plc?

Thanks

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**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [May 22, 2019, 5:57pm UTC](https://forum.inductiveautomation.com/t/optimise-data-access-on-siemens-plc/25237/2 "2019-05-22T17:57:23Z")

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The only reason it would matter if you created separate scan classes is if you wanted to poll the data at different rates.