Using interactive batch mode is not necessarily a good citizen on the MTL, given the limited number of exclusive batch nodes available and the option of specifying long batch run duration.
So as not to excessively block other users from running (scripted) batch jobs, a hard walltime limit, has now been imposed for all interactive jobs. This hard limit is currently set to two hours, i.e. 2:00:00. Any interactive job submitted with a walltimebeyond this hard-limit, e.g.
$ qsub -l select=1:ncpus=32 -l walltime=02:01:00 -I
will automatically fail to execute and generate the message:
qsub: Job exceeds queue and/or server resource limits
It is strongly suggested that interactive batch runs only be submitted when PBS scripting does not work as it is very easy to tie up an idle batch node, while waiting for interactive shell input.