How to shrink the IRISTemp database

InterSystems FAQ rubric

You can set the maximum size of the IRISTemp database at IRIS startup by setting a configuration parameter called MaxIRISTempSizeAtStart.

After setting, the system will truncate IRISTemp to the set value (MB) at the next IRIS startup. If the current size is less than the specified MaxIRISTempSizeAtStart, no truncation will occur. Also, if 0 is specified, truncation will not be performed, so the size will start without changing. (Default) Settings are made from the menu below.

Management Portal
[System Administration] > [Configuration] > [Additional Settings] > [Start] > "MaxIRISTempSizeAtStart"

For details, please check the documentation page below.
MaxIRISTempSizeAtStart