In a recent tip, I discussed the use of variable length fields in building strings within RPG programs. This time, I will focus on how these fields can be utilized in our databases and consider the trade-offs, between disk space and performance, involved.

Why would you want to use a variable length field? Well, how about product descriptions as one example, or notes fields associated with an order? The marketing department would probably like to have an unlimited number of characters to play with, but they may accept a limit of say 1,000 as more realistic. The problem, of course,

In the factory where I work, we are replacing one engineering module of the large ERP package we run with a more modern, more robust engineering module. What was one physical file is now two or three physical files. Modifying programs and queries to use the new files is just about more fun than I ever envisioned when I was learning to write RPG at the vo-tech many years ago. Fortunately, I have some great tools to help with the conversion. One of them is the common table expression. I’ll show you what I mean.

Assume a customer master file,

Vigilance pays, negligence punishes. Want proof? Try ignoring i5/OS message CPI1468 (System job tables nearing capacity) the next time it shows up. A system job table overflow can prevent your system from accepting new jobs, delete your spooled files, fill up your DASD, or stop an IPL. And those are its good points. This week and next, I’ll look at system job table overflows and how they affect your system.

What Are System Job Tables and Why Should I Care?

System job tables are internal system objects used by the i5/OS operating system to track every job on a partition.