I don't know either which AIX version your customer runs, but there is a BIG chance it isn't AIX 5.3 of any sort at all. 5.3 is not supported any more since a some years now (even its successor 6.1 is almost out of support) and on newer (POWER8) systems it won't even run. On the other hand the recent AIX version (7.2) will not run on POWER5 or even POWER6 platforms.

From 5.3 to 6.1 and from 6.1 to 7.1 there were two big changes and - lacking intimate knowledge of your application - it is quite conceivable that your code might have problems running on current platforms and/or OS versions.

To what agent.kgb (rightfully) said i'd like to add: get a current platform to compile your software, POWER7 at least or preferably a POWER8.

I hope this helps.

bakunin