There is no limitation to how many requirements can be added to jobs--however, there are a couple of caveats.
1. Prior to r12, only 255 of any type requirement (data set, job, user, etc) can be listed -- though all requirements are added, they will not all be listed under all circumstances.
2. If a job enters the request queue with more than 255 OUTSTANDING requirements, there can be unpredictable results when the requirements are posted. This is due to a 'counter' in the job's queue record for number of unsatisfied Master Requirements which holds only up to 255. To handle the possibility of this happening you can use RQMT255=YES on the OPTIONS statement in the initialization file. Using this keyword causes a WTO (CA-7.SFER-08) to be produced, and builds a special user requirement that has to be manually posted for any job that has more than 255 UNSATISFIED requirements.