If the mail store is handling lots of mailboxes and messages per second then you may want to increase the number of ims_master processes that job_controller will start to process the ims-ms queue. To increase the number of processes you need to make two changes, one in the imta.cnf file and the other in the job_controller.cnf file. In the imta.cnf file you need to change the maxjobs keyword, in the job_controller.cnf file you need to adjust the job_limit for the IMS_POOL.