Session Title:  15 Ways of Accessing Data by Key 

Presented By: Kaare Plesner

Commercial applications written in RPG or COBOL use on average more run time on I/Os than on any other activity. Reading accounts for over half of the I/Os, and very often a program needs to locate and read a record or row based on a key value.

This presentation shows the CPU and elapsed time used by 15 different methods for keyed access to a data base. The most commonly used program code appeared to run four times slower than the most efficient.

Our objective is to discuss when to use which access method and how to identify “low hanging optimization fruits”. We also show some incredibly efficient alternatives that are mainly unknown but easy to use. Changing program code to use a more efficient I/O method may reduce run time significantly and is very straightforward because it doesn’t interfere with the main logic of the program.