Application optimization in DB/DC and DCCTL environments

To reduce the amount of read I/O to the ACBLIB data set, consider loading the ACB members into 64-bit storage by specifying ACBIN64=ggg in the DATABASE section of the DFSDFxxx PROCLIB member. When the application is scheduled, the ACB members are retrieved from 64-bit storage instead of from the ACBLIB data set.

If possible, avoid the use of overlays in message processing programs. An exception might be if the application program uses large blocks of code exclusively for part of the transaction processing.

Do not have application programs that perform non-DL/I functions (such as STIMER and TTIMER, and contents supervision). Unless carefully controlled, such application programs usually perform poorly.

If lengthy application programs must be initiated online, consider splitting the application into two parts: an interactive part, which responds to the user and sends a program-to-program message to a batch part, which can be run in a low-priority region.

Consider redesigning applications whose performance is critical. Otherwise, plan to tune the system to process the transaction as it is before embarking on a total rewrite. Consider translating applications whose performance is critical from high-level language to assembler in order to improve program-load and execution time.

Always use the rollback (ROLB) call rather than cause the program to abnormally terminate. This keeps the message region available without operator intervention and with a smaller delay in message region availability to other transactions. (Abnormally terminating an application program keeps the region unavailable to other transactions waiting to be scheduled.)