We have turned on backfill scheduling on Improv, Bebop and Swing. This will be a lowest priority queue where users can run once their allocation has been used up. We are going to start with backfill jobs having a maximum walltime of 4 hours, which we hope balances some useful computing time with not blocking normal production jobs too much. To use backfill, you will have to explicitly set your queue to backfill and walltime to 4 hours or less when you submit a job. Jobs will not automatically move from normal compute queue to backfill when you use up your allocation.]

Note that you can override PBS job script settings at the command line.  For example if you have your queue set to compute and walltime to 24 hours in your job, you can do the following to override script and run in backfill:

qsub -q backfill -l walltime=4:00:00   <your PBS script>