# Modbus problem ReadHoldingRegisterRequest

**URL:** <https://forum.inductiveautomation.com/t/modbus-problem-readholdingregisterrequest/22414>\
**Category:** Ignition\
**Created:** [February 7, 2019, 1:55pm UTC](https://forum.inductiveautomation.com/t/modbus-problem-readholdingregisterrequest/22414 "2019-02-07T13:55:46Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![denis.palomanes](https://avatars.discourse-cdn.com/v4/letter/d/779978/32.png) [@denis.palomanes](https://forum.inductiveautomation.com/u/denis.palomanes)\
**Post date:** [February 7, 2019, 1:55pm UTC](https://forum.inductiveautomation.com/t/modbus-problem-readholdingregisterrequest/22414/1 "2019-02-07T13:55:46Z")

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Hello,

We have 77 modbus devices and we are reading about 70.000 tags and sometimes we have some warnings “ReadHoldningRegistersRequest” and “TimeoutDaemon”.

What can be the problem?

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/2X/3/385fe22d77eb3a3353aa78792920f64cb6839035.png)

Thank you,

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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:** [February 7, 2019, 2:40pm UTC](https://forum.inductiveautomation.com/t/modbus-problem-readholdingregisterrequest/22414/2 "2019-02-07T14:40:30Z")

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These happen when a response to a request isn’t received within the configured timeout.

It looks like you might be experiencing these for multiple devices at once, which would suggest some kind of temporary network interruption or something like that.

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**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [February 7, 2019, 9:47pm UTC](https://forum.inductiveautomation.com/t/modbus-problem-readholdingregisterrequest/22414/3 "2019-02-07T21:47:50Z")

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> [@Kevin.Herron](#):
>
> some kind of temporary network interruption or something like that.

Or a java pause-the-world. What version of Ignition is this, and is it using G1GC?

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**Author:** ![denis.palomanes](https://avatars.discourse-cdn.com/v4/letter/d/779978/32.png) [@denis.palomanes](https://forum.inductiveautomation.com/u/denis.palomanes)\
**Post date:** [February 8, 2019, 11:40pm UTC](https://forum.inductiveautomation.com/t/modbus-problem-readholdingregisterrequest/22414/4 "2019-02-08T23:40:19Z")

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Hello,

We are using Ignition 7.9.7. and the garbage collector are:

![image](https://us1.discourse-cdn.com/inductiveautomation/original/2X/6/6de6541a334fdc8021be4ddf1fc264b4b86c79d5.png)

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**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [February 9, 2019, 2:35am UTC](https://forum.inductiveautomation.com/t/modbus-problem-readholdingregisterrequest/22414/5 "2019-02-09T02:35:36Z")

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Yeah, search this forum for “G1GC” for lots of suggestions, many from me. (-: