EBS upgrade process from 12.1 to 12.2.X High Level Steps....

R12.1 to R12.2:  upgrade process:High Level Steps

R12.2. upgrade process:

1. Preapare and plan for upgrade with documentaion.
2. Database upgrade: select latest version of database else if you are on 11g then min 11.2.0.3 version should be availbale.(ETCC DB utility-checkMTdb.sh)
3. apply latest PSU patches on Grid/database .
4. Backup you whole system including application and database (which include custom.pll and custom.plx from $AU_TOP)
6. All custom database objects that are mapped to seeded APIs/Row Handlers must be changed from LONG/LONG RAW to CLOB.
5. Run Gather Schema statistics on current system.
6. Download software for upgrade from edeliver.oracle.com and unzip it.
7. run buildStage.sh and create staging area for R12.2
8. Enable maintenance mode and Start installation of Application of R12.2.0 as a root user.
9. select upgrade option in wizard and complete installation.
10.Apply AD R12.2 and CPU Upgrade patches, merge all patches and apply it.
11. Configure Release R12.2 E-Business Suite Instance . Update the RDBMS ORACLE_HOME file system with Auto Config and Clone files.
12. Run Rapid Install to configure Release 12.2 E-Business Suite instance,You must run Rapid Install a
    second time to complete the configuration using Run File System context file.
13. use Adsplice for custom schema register .
14. Enable Online Patching- Readiness Reports (ADOP), Installing the ETCC Patches on DB Tier and application tier.
15. check Online Patching Enablement - Status Report , check for any corruption or code violation.
16. Apply latest technology AD and TXK patches of Delta
17. start fresh patch cycle and apply the Upgrade patch  from R12.2.0 to R12.2.6/7 patch
18. Language patch : if there are multiple lageuages are there then we need apply transaltion patches ie. TSP (traslation sync patches)
19. Customization: we need to take care of customization from old versions . need to follow development standards and deploy it.
20. Do the sanity checks and release the instance.

Thanks
Srini