logged in as the application user, can you create a file under /home/oracle/apps/apps_st/appl/admin/PROD
Is this a NFS mounted filesystem?
Check all permissions of all directories starting with /home
ls -ld /home
ls -ld /home/oracle
ls -ld /home/oracle/apps
ls -l /home/oracle/apps/apps_st
ls -l /home/oracle/apps/apps_st/appl
ls -l /home/oracle/apps/apps_st/admin
Issue is the mount point, We moved to another location..it works now.