Specifies the size of each Java thread's execution stack. You may need to increase the default number of bytes if you need deeply-nested call stacks, but otherwise you should not need to change the default.
409600 (bytes, which is 400KB)
Don't set this value below 204800 (200KB) or above 819200 (800KB)
In order for changes to this setting to take effect, the JVM must be restarted. Therefore, the Domino server needs to be restarted.
Lotus Notes/Domino Notes.ini settings
Domino Configuration Tuner:
This setting is included in the DCT catalog of best practices as of Domino 8.5