How adpatch will apply at external tier at ebiz R12

Hi Team,

Customer wants to apply one adpatch both at internal tier and exteral tier[DMZ]. Their current architechture is as below

a) Both the external and internal are at same server.
b) Both tier has the different mount point for external and internal.

My question is
1. What will be sequence at the time of applying the patch
2. At the time of applying the patch at external tier, do the patch update the data at Database again? if it is already applied at internal tier. 

Regards,
Rasheed