How to disable back pressure inside Exchange

How to disable back pressure inside Exchange

^{Created: 2019-05-15 05:49:07 | Last modified: 2022-12-01 23:18:53} ^{| By: Nova}
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How to disable back pressure inside Exchange, this has been used as a temporary solution for when the error message "452 4.3.1 Insufficient system resources"

How to disable back pressure inside Exchange, this has been used as a temporary solution for when the error message "452 4.3.1 Insufficient system resources". We have seen this happen when disk spaces gets below a certain value, CPU runs too high etc. In 2007-2013 versions changing the back pressure value has been enough, however for 2016 and 2019 we have found that we also need to move the queue to a larger volume.

You can verify there is a back pressure issue by running the following Exchange Shell Command

[xml]$bp=Get-ExchangeDiagnosticInfo -Process EdgeTransport -Component ResourceThrottling; $bp.Diagnostics.Components.ResourceThrottling.ResourceTracker.ResourceMeter

# In this example we can see that 89% and 90% pressure has been applied because of Disk space in the Queue and data folders

Resource            : DatabaseUsedSpace[C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\data\Queue]
CurrentResourceUse  : Low
PreviousResourceUse : Low
PressureTransitions : [PressureTransitions: MediumToHigh=99 HighToMedium=97 LowToMedium=96 MediumToLow=94]
Pressure            : 89

Resource            : UsedDiskSpace[C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\data\Queue]
CurrentResourceUse  : Medium
PreviousResourceUse : Medium
PressureTransitions : [PressureTransitions: MediumToHigh=98 HighToMedium=94 LowToMedium=90 MediumToLow=88]
Pressure            : 90

Resource            : UsedDiskSpace[C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\data]
CurrentResourceUse  : Medium
PreviousResourceUse : Medium
PressureTransitions : [PressureTransitions: MediumToHigh=99 HighToMedium=94 LowToMedium=90 MediumToLow=88]
Pressure            : 90

Open C:\Program Files\Microsoft\Exchange Server\V??\Bin\EdgeTransport.exe.config edit the following keys (you may need to remove the first space after < as this site doesn't allow tags)

To disable back pressure add the following to the keys section

< add key="EnableResourceMonitoring" value="false" />

Restart transport service

net stop MSExchangeTransport
net start MSExchangeTransport

To move the queue. Stop the Exchange Edge Transport service, add/modify the following key, confirm the directory and permissions are correct, start the service again.

< add key="QueueDatabasePath" value="D:\Queue\QueueDB" />