There was os level patch which create this issue ,,but it seems only uniface application are giving this issue .. below is response from AIX IBM team.

This literally screwed our server .

uniface patch           :- Uniface 9.4.01 r113

 AIX oslevel patch    :-  6100-06-05-1115

Response from AIX team

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The hang situation can be due to exit() being called in function registered by atexit(),
if that's the case, then the fix, from application side, is not to call
exit() in function registered with atexit(), the function shall just return.

In other situation, the hang can been seen when exit() is called from a signal handler.

The problem was injected by change in IZ71004 at TL06 base level,
or 6.1.5.6, or 6.1.4.9, that's why citi's other/earlier levels do not have it.

From stacks in pdump output, we do not see two exit() calls, possibly because pdump
by default only collects kernel stack while application was in user space code.
However, thread 2589 does seem to be in a signal handler.

Can you confirm from the application side (if you have access to application owner or code),
whether this application calls exit() from one of the two places I mentioned?

Please let us know if some one has idea about it.

This hang might be due to something else. Since atexit is not used and I think also not from a signal handler.

Sometimes database client software uses this to logoff from the DB before the application exits.

Did you also upgraded to a new version of sybase? Consider making a support call.

AIX was migrated to patch    :-  6100-06-05-1115 , which caused this issue.

We have rolled back the patch in prod hence now the issue is not in prod but we need to find a solution for this one.

None of the other application has this issue , only uniface gives this issue so i think some changes need to be done in uniface part.

Good Luck