How to apply ad patches on Oracle EBusiness Suite R12

Quick steps to apply patches ->

1. Download the patch from metalink and transfer it to the patches directory 
   of the instance.
2. Shutdown The Application: Go to $INST_TOP/admin/scripts and run adstpall.sh
3. Enable Maintenance mode: Go to $APPL_TOP, execute application environment file (one named like APPS_hostname) then run adadmin. Go to change maintenance mode and enable it and come out of adadmin.
4. Run adpatch. Put all values as asked.
5. Give the no of workers; it may be double of the no of CPUs.
6. To monitor the status of the workers, there is a utility called ‘adctrl’. Run this from $APPL_TOP after executing the application env file in another session to monitor the worker status while applying patches.
7. After the patch application is over, disable the maintenance mode in the same way.
8. To be in safe side restart the Database once.
9. Make the application up and check if con managers are running.