Exclusive scheduling gives a job exclusive use of the host that it runs on. LSF dispatches the job to a host that has no other jobs running, and does not place any more jobs on the host until the exclusive job is finished.
Compute unit exclusive scheduling gives a job exclusive use of the compute unit that it runs on.
When an exclusive job (bsub -x) is submitted to an exclusive queue (EXCLUSIVE = Y or =CU in lsb.queues) and dispatched to a host, LSF locks the host (lockU status) until the job finishes.
LSF cannot place an exclusive job unless there is a host that has no jobs running on it.
To make sure exclusive jobs can be placed promptly, configure some hosts to run one job at a time. Otherwise, a job could wait indefinitely for a host in a busy cluster to become completely idle.
For pending allocation requests with resizable exclusive jobs, LSF does not allocate slots on a host that is occupied by the original job. For newly allocated hosts, LSF locks the LIM if LSB_DISABLE_LIMLOCK_EXCL=Y is not defined in lsf.conf.
If an entire host is released by a job resize release request with exclusive jobs, LSF unlocks the LIM if LSB_DISABLE_LIMLOCK_EXCL=Y is not defined in lsf.conf.
Jobs with compute unit resource requirements cannot be auto-resizable. Resizable jobs with compute unit resource requirements cannot increase job resource allocations, but can release allocated resources.