A conditional job dependency is indicated by prefixing the predecessor job name with a question mark (?). If job A is conditionally dependent on job B, then job A will depend on job B only if job B is in the request, ready, or active queues when job A enters the request queue.
A job predecessor requirement defined as conditional (?) is considered satisfied if it is NOT in the request, ready, or active queue when the requiring job enters the request queue. Otherwise, the predecessor job is considered an unsatisfied requirement. Also, a conditional requirement can establish only one requirement per job even if multiple occurrences are in the queues for the other job.