When a job is dispatched, the system assumes that the resources that the job consumes will be reflected in the load information. However, many jobs do not consume the resources they require when they first start. Instead, they will typically use the resources over a period of time.
For example, a job requiring 100 MB of swap is dispatched to a host having 150 MB of available swap. The job starts off initially allocating 5 MB and gradually increases the amount consumed to 100 MB over a period of 30 minutes. During this period, another job requiring more than 50 MB of swap should not be started on the same host to avoid over-committing the resource.
You can reserve resources to prevent overcommitment by LSF. Resource reservation requirements can be specified as part of the resource requirements when submitting a job, or can be configured into the queue level resource requirements.
When deciding whether to schedule a job on a host, LSF considers the reserved resources of jobs that have previously started on that host. For each load index, the amount reserved by all jobs on that host is summed up and subtracted (or added if the index is increasing) from the current value of the resources as reported by the LIM to get amount available for scheduling new jobs:
available amount = current value - reserved amount for all jobs