1. A method of tracking real time use of I/O control blocks on a processing unit basis in a multiprocessing computing system including a plurality of processing units, the method comprising: assigning a task control block to each of the processing units; each of the processing units, locking I/O control blocks for exclusive use by the processing unit; and for each of the processing units, identifying in the task control block assigned to the processing unit, the I/O control blocks locked by the processing unit.