Generally, a few DFSORT applications at a site can be identified as being the largest and longest running, or on a critical path. An application is said to be on a critical path if any delay in its completion would delay finishing the workload. Tuning activities on the critical path can have a beneficial effect in reducing the overall elapsed time of the batch workload. The performance of these applications can determine whether you finish inside the batch window or overrun it, or whether you are using too many system resources. The "80/20 rule of thumb" applies to DFSORT: often 80% of the system's resources used by DFSORT are used by 20% of DFSORT applications.

Start your investigation by concentrating on these applications. Use a SORTDIAG DD statement (or make sure the ICEMAC option DIAGSIM=YES has been specified for your site) to obtain all available messages.

DFSORT messages are a simple and effective source of information for individual applications. They give you a picture of the processing and help you develop an action plan.