thanks scott, bakunin for your replies.
By changes in the system, I meant any s/w updates, OS level updates made in some specified period of time.
My program is not changed in last few months. If I build the same code now, it does not work as expected.
I am using some third party s/w integrated in my code, but even that is not changed.
So my guess is something changed in AIX system that is affecting my program in a bad way.
We have found a solution to this now. If I change third party call(which was working earlier fine) my program works now.
I find AIX miserable always
thanks for all your help/comments.
Ashish