Imagine not being allowed to code *FIRST in the MBR parameter of the Override with Database File (OVRDBF) command. Horrible thought, isn’t it? Special values make commands more sensible and easy to use. Here are 10 facts every IBM i developer should know in order to effectively use special values in his own commands.

1. Special values are character strings that are incompatible with validity checking rules. In this example, BATCH requires a three-digit number, and *ALL does not fit that description.

PARM  KWD(BATCH) +
      TYPE(*DEC) LEN(3 0) +
      DFT(*ALL) +
      REL(*GT 0) +
      SPCVAL((*ALL -1)) +
      PROMPT('Batch number')</all>

2.

We had a recent crisis in our shop. When we dug to the root of the problem, we found that one of our files had an invalid value in one of the fields. I don’t understand why this was the case, because the programmer who wrote the DDS used the VALUES keyword on the field in question. Does the VALUES keyword not prevent invalid data from entering the database?

–Paul

No, Paul. One would think it does, but use of the VALUES keyword only applies to the workstation controller. That is, only the green-screen interface is restricted by the VALUES

I want to run the i OS Performance Adjuster to automatically allocate system memory to my subsystems. But when I turn it on, most of the memory goes to the *INTERACT storage pool used by the QINTER subsystem. I want to take care of interactive users, but I also want some memory left over for other subsystems. How do I limit *INTERACT from using too much memory?

–Jens

This sometimes happens with using the i operating system automatic performance adjustment feature. By default in the i 6.1 operating system, the Performance Adjustment (QPFRADJ) system value is set to “2”. This