EBS-- 12.2 Applications Dba Online Patching (ADOP)

Online patching is our new toy in EBS 12.2.
Adop is the utility for patching EBS 12.2 . Adop replaces adpatch, altough it uses adpatch in background :)
Oracle provides this online patching system by using two Apps tier filesystems named fs1 and fs2 in Application tier , by using edition based redefinition feature of 11gR2 Rdbms in Database Tier.
Normally, we have 5 phases when applying a EBS patch. These phases are prepare,apply,finalize,cutover and cleanup. (adop phase=..)

We start with prepare for syncronizing the patch filesystem for Applications and the patch version for db tier.
Then we continue with apply phase. This phase is actual phase that the patch operations are done.. adop uses patch filesystem to upload new apps tier files and uses the patch edition of the database to take db actions.  After apply we continue with adop=finalize. In this phase, application and database specific actions such as compilation takes place.
So those 3 phases require no downtime , but the next phase which is called cutover need a little downtime. It is automatic though.. In cutover phase, adop switches the patched filesystem and db edition with the current/run filesystem and db edition... That's why Application Tier components are restarted in this phase.. Downtime is coming from restarting the components..
The last phase is cleanup phase. It is self explanatory..  In this phase ADOP starts cleaning up the old editions.

One last thing, if you are using 12.2.0 VISION, be careful if you need to restart the apps tier process after a patch application, because in 12.2 VISION we dont have an environment file for choosing and setting the correct environment.. I mean EBSapps.env..
On the other hand, you can use the following script maybe;

# Script to set the current RUN Edition APPL_TOP environment automatically.
# Available through My Oracle Support Note 1545584.1
# Requirements: Set the XMLfile variable as specified below. This needs
# to be set only once and not again after a file system cutover in adop.
# Save the script as fsauto<SID>.env in a non-EBS directory, eg.:
# /home/oracle/fsautoPROD.env
# Usage: . <directory>/fsauto<SID>.env
# Eg.: . /home/oracle/fsautoPROD.env
# note the space ' ' character between the leading period '.' and first
# forward-slash '/' characters
# Alternatively use: source <directory>/fsauto<SID>.env
# If needed make the script runnable using command: chmod u+x fsautoPROD.env
# Carlo den Otter, 02-APR-2013
# Note this script is for educational purposes only, and as such is not supported.
# It was created on Linux and not tested on other platforms.
# Use at own risk.

Lastly, I suggest you to take a look to the following note for the environment setting :
How To Automatically Set the Current Run or Patch Edition / File System for EBS 12.2 (Doc ID 1545584.1)


One last thing.. I share a drawing of mine , that explains this online patching process.. Maybe it become useful for understanding..