<bsub_options> are options for the job restart. See the Platform LSF Reference guide for a complete list with descriptions.

<checkpoint_directory> specifies the checkpoint directory where the job subdirectory is located.

<job_ID> is the job ID of the Fluent job, and specifies which job to restart. At this point, the restarted job is assigned a new job ID, and the new job ID is used for checkpointing. The job ID changes each time the job is restarted.