Tuning the Teleprocessing Environment

Tuning your teleprocessing environment is essential to ensure that your online transactions are running in an optimal fashion. DB2 can use any of the three teleprocessors supplied by IBM: CICS, IMS/TM, and TSO. The tuning advice is different for each.

In this section, I do not provide in-depth tuning advice for your teleprocessing environments. An entire book could be devoted to the tuning of CICS, IMS/TM, and TSO. Your shop should ensure that the requisite level of tuning expertise is available. However, you should keep in mind several basic online tuning strategies. The following guidelines are applicable for each teleprocessing environment supported by DB2.

Limit Time on the Transaction Queue

Tune to limit the time that transactions spend on the input queue and the output queue. This way, you can decrease overhead and increase response time.

Design Online Programs for Performance

Ensure that all the program design techniques presented in Chapter 18, "The Doors to DB2," are utilized.

Store Frequently Used Data in Memory

Place into memory as many heavily used resources as possible. For example, consider using data spaces for CICS tables.

Make Critical Programs Resident

Consider making programs for heavily accessed transactions resident to reduce the I/O associated with loading the program. A resident program remains in memory after the first execution, thereby eliminating the overhead of loading it each time it is accessed.

Buffer All Non-DB2 Data Sets

Ensure that all access to non-DB2 data sets (such as VSAM or IMS) is buffered properly using the techniques