what happens in cutover phase of adop in R12.2:

 Cutover phase of adop is downtime phase of Online patching cycle. Once cutover is complete, it is not possible to revert to the previous edition.

Cutover phase  of adop has following steps:

1.Shut down internal concurrent manager: 

cm_wait=<maximum_minutes_to_wait> 

$FND_TOP/bin/txkADOPCutOverPhaseCtrlScript.pl script

2.Shut down application tier services:

$FND_TOP/bin/txkADOPCutOverPhaseCtrlScript.pl script

3.Cutover database: Promote patch database edition to become the new run database edition, using adzdpmgr.pl script.

This task is performed by $FND_TOP/bin/txkADOPCutOverPhaseCtrlScript.pl script 

4.Cutover file system: Promote patch file system to become the new run file system, switching the $FILE_EDITION values in the patch and run enviroments. The current patch APPL_TOP becomes the new run APPL_TOP, and the current run APPL_TOP becomes the new patch APPL_TOP.This task is completed by Autoconfig.

5.Terminate old database sessions: Terminate any database connections to the old run edition of the database.

This task is performed by $FND_TOP/bin/txkADOPCutOverPhaseCtrlScript.pl script

6.Start application tier services: Application tier services are restarted, on the new run edition. The system is now available again to users.

This task is performed by $FND_TOP/bin/txkADOPCutOverPhaseCtrlScript.pl script

Refrence:

https://techgoeasy.com/happens-cutover-phase-adop-r12-2/