How long can memory leaks persist in RPGLE programs?

Question

I'm putting into production some RPGLE code which uses %alloc and dealloc to allocate memory. Programmers should be able to ensure there are no resulting memory leaks but I'm worried about what happens if they don't.

My question is: if programmers mess up and there are memory leaks then when will this memory be reclaimed? Is it when the program leaves memory or when the job finishes?

Answer 1

I am not familiar with those built-in-functions, but normally everything is cleaned up when the job ends (or user logs off if interactive). If you can't find an answer, I can point you to another community were your answer may be known.

Answer 2

From the ILE RPG Programmer's Reference Guide:

Storage is implicitly freed when the activation group ends. Setting LR on will not free any heap storage allocated by the module, but any pointers to heap storage will be lost.

If your RPG program is in its own activation group, then the memory will be freed when the program ends. Of course, when your job ends, so does your activation group. So ending the job will always clean up any memory allocated.

Answer 3

It sounds like you are approaching RPG from a C/C++ background. I've been programming in RPG for about 8 years now and only a handful of times ever had to use the %alloc() BIF.

That being said if you are using a new activation group, you should be fine. If you are using a named activation group and you do not issue the RCLACTGRP command or you are using the default activation group you could run into issues.

Answer 4

Indeed, you have to study the mechanism of activation groups. Memory leaks may happen, but will not do any damage to the machine (I love the as400). But you can harm the other programs within your iSeries job (remark: if you are not from a as400 background, you have to read about the as400 job mechanism).

If you start with managing the activationgroups within your job yourself (in the program that is ofcourse), you can create separate, sort of memory area's. It requires some overhead (you have to name the groups) but then you have a safe environment where you can powerfull stuff.