# Tag limits when using Siemens Enhanced Driver

**URL:** <https://forum.inductiveautomation.com/t/tag-limits-when-using-siemens-enhanced-driver/111662>\
**Category:** Ignition\
**Tags:** siemens, ignition83\
**Created:** [October 22, 2025, 7:08pm UTC](https://forum.inductiveautomation.com/t/tag-limits-when-using-siemens-enhanced-driver/111662 "2025-10-22T19:08:28Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![ian2](https://avatars.discourse-cdn.com/v4/letter/i/dec6dc/32.png) [@ian2](https://forum.inductiveautomation.com/u/ian2)\
**Post date:** [October 22, 2025, 7:08pm UTC](https://forum.inductiveautomation.com/t/tag-limits-when-using-siemens-enhanced-driver/111662/1 "2025-10-22T19:08:28Z")

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Hi all, I have been testing Ignition’s [Siemens Enhanced driver](https://www.docs.inductiveautomation.com/docs/8.3/ignition-modules/opc-ua/opc-ua-drivers/siemens/siemens-enhanced-driver) for symbolic access to optimized DBs in an S7-1500 PLC via S7 communication and have found it to work quite well. My only question is I cannot seem to find any documentation on what the maximum tag / subscription count is when using this driver and am wondering where I can find this information. I already reached out to my Siemens sales rep and they said it would depend on exactly how Ignition is communicating to the PLC, hence I am asking here.

Thank you in advance!

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**Author:** ![Cody\_Morgan](https://avatars.discourse-cdn.com/v4/letter/c/db5fbb/32.png) [@Cody\_Morgan](https://forum.inductiveautomation.com/u/Cody_Morgan)\
**Post date:** [October 22, 2025, 8:28pm UTC](https://forum.inductiveautomation.com/t/tag-limits-when-using-siemens-enhanced-driver/111662/2 "2025-10-22T20:28:59Z")

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Hi @ian2,

There is no hard limit for tag/subscription count on the Ignition driver side. As far as I know, there's not a hard set limit on the PLC either. You can theoretically subscribe to every tag on the PLC. That being said, the driver may not be able to read those tags as quickly as you would like. How many tags you can read at a one second scan rate can vary drastically based on your environment. For example, you may be able to read ~15,000 tags per second when the gateway sits very close (\<1ms ping) to the PLC. That number may drop to ~3,000 tags per second when introducing 30-60ms of latency.

We're working on being able to provide some test results from our in house testing environment so that users will have _some_ idea of performance. However, as I mentioned before, this performance can vary drastically based on your environment (network latency, tag types, PLC resource, PLC load, etc.). So, we are also working on providing some metrics to help users understand how the driver is performing in their specific environment.

Would you be willing to share more about your use case? Number of tags, desired rate, etc.

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**Author:** ![ian2](https://avatars.discourse-cdn.com/v4/letter/i/dec6dc/32.png) [@ian2](https://forum.inductiveautomation.com/u/ian2)\
**Post date:** [October 23, 2025, 12:54am UTC](https://forum.inductiveautomation.com/t/tag-limits-when-using-siemens-enhanced-driver/111662/3 "2025-10-23T00:54:05Z")

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I see, thank you for the detailed response! I will do my own internal testing but am very curious to see your results.

This project has ~50,000 tags split between 3 PLCs, hoping for 1s refresh rate on the bulk of them but probably 10,000 of them can be 5s+ for less critical monitoring. The plan is for a fiber ring network connecting the PLCs to each other and to the Gateway host, all within the same 0.5 sq. mile. I’m primarily hoping that I don’t need to buy more PLCs solely to communicate more tags.

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**Author:** ![Cody\_Morgan](https://avatars.discourse-cdn.com/v4/letter/c/db5fbb/32.png) [@Cody\_Morgan](https://forum.inductiveautomation.com/u/Cody_Morgan)\
**Post date:** [October 23, 2025, 5:05am UTC](https://forum.inductiveautomation.com/t/tag-limits-when-using-siemens-enhanced-driver/111662/4 "2025-10-23T05:05:35Z")

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FWIW, in the testing I've done so far, the bottleneck seems to be on the PLC side. If you have decently capable PLCs, this might be doable.

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**Author:** ![ian2](https://avatars.discourse-cdn.com/v4/letter/i/dec6dc/32.png) [@ian2](https://forum.inductiveautomation.com/u/ian2)\
**Post date:** [April 6, 2026, 11:34pm UTC](https://forum.inductiveautomation.com/t/tag-limits-when-using-siemens-enhanced-driver/111662/5 "2026-04-06T23:34:42Z")

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Reviving this thread to say I migrated 9000 tags over to the Siemens enhanced driver and left ~20,000 on OPC-UA and have not noticed any performance issues in the last 4 months. Have there been any updates with IA’s internal test results?

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**Author:** ![nminchin](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nminchin/32/6911_2.png) [@nminchin](https://forum.inductiveautomation.com/u/nminchin)\
**Post date:** [April 7, 2026, 12:58am UTC](https://forum.inductiveautomation.com/t/tag-limits-when-using-siemens-enhanced-driver/111662/6 "2026-04-07T00:58:38Z")

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You’ve got 20k tags subscribed to the PLC’s onboard OPC-UA server? what PLC and update rates do you have configured? I was under the impression that the PLC would fall over with this number of tags if this was polling at a reasonable rate (i.e. every 1-2s)

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**Author:** ![ian2](https://avatars.discourse-cdn.com/v4/letter/i/dec6dc/32.png) [@ian2](https://forum.inductiveautomation.com/u/ian2)\
**Post date:** [August 3, 2026, 11:15pm UTC](https://forum.inductiveautomation.com/t/tag-limits-when-using-siemens-enhanced-driver/111662/7 "2026-08-03T23:15:14Z")

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Sorry for the year+ delay. Yes, currently the PLC is only monitoring 9161 tags but this is because I moved 9385 of them over to a new tag provider on the enhanced driver. At its peak the PLC was handling 18,546 tags all on OPC-UA in parallel with 9385 duplicated on enhanced driver. Have not had any issues with 9161 tags on the enhanced driver.

PLC is a 6ES7 517-3AP00-0AB0 (1517, PN/DP). ~50% of the tags are on 1s update rate, the rest are anywhere from 5-30 seconds.