AIX - During adstrtal.sh getting "Database connection could not be established. Either the database is down or the APPS credentials supplied are wrong"

In AIX machine - We have encountered an issue where while starting application services we are getting issue

Database connection could not be established. Either the database is down or the APPS credentials supplied are wrong

We did below things:

1) PING is working fine from APPS to DB and DB to APPS

2) TNSPING is working fine.

3) Able to login sqlplus from application node using /nolog and apps user, so apps user password is not an issue.

4) Did DB and Listener bounce

5) Autoconfig on DB and Apps

6) DBC file also looks OK 

In our case issue was with /tmp, someone did something and applmgr user unable to create any file on this location:

$ touch aa

touch: 0652-048 Cannot change the modification time on aa.

Chnage the permission of /tmp to 777 and then user applmgr able to write it.

Application came up fine.

Thanks,