The amount of memory a job requires should be given in the job control script. Care must be taken to specify the value as accurately as possible.

If the value given is too high, then

• the job may have to wait longer than necessary before enough memory is available.
• once the job starts, other jobs may have to wait, because although memory is available, it has been reserved for the running job. In the illustration below, although enough cores are available, the job shown cannot start because the queueing system cannot reserve enough memory on the node.

If the value is too low, then

• the job will be terminated once its memory requirement exceeds the amount of memory requested