ADOP Failes with "Unable to find appltop_id for the host from database"

Issue:

Our EBS 12.2 application has been cloned recently from PROD and this is a shared application tier. User requested to apply a patch and when we tried to apply the patch adop is coming with errors. Below are the error details.

[UNEXPECTED]Unable to find appltop_id for the host oraap02 from database
[UNEXPECTED]Unable to find appltop_id for the host oraap02 from database
[EVENT]     [START 2015/04/10 02:23:17] Verify SSH
Logfile location /u01/app/fs1/inst/apps/EBSR12_shared/logs/appl/rgf/TXK/verifyssh.log
xml output = /u01/app/fs1/inst/apps/EBSR12_shared/logs/appl/rgf/TXK/out.xml
[EVENT]     [END   2015/04/10 02:23:20] Verify SSH
All nodes have ssh connectivity. Continuing...
[EVENT]     [START 2015/04/10 02:23:20] Checking the DB parameter value
[EVENT]     [END   2015/04/10 02:23:23] Checking the DB parameter value  [UNEXPECTED]Unable to find appltop_id for the host oraap02 from database
  [UNEXPECTED]Invalid appltop id: "".
  [UNEXPECTED]Unrecoverable error occured. Exiting the current session.
  Log file: /u01/app/fs_ne/EBSapps/log/adop/adop_20150410_022145.log

The above error doesn't give much clear information on what was causing issue. I started reviewing & validating the below tables and everything shows good.

FND_NODES
FND_OAM_CONTEXT_FILES
AD_APPL_TOPS
AD_ADOP_SESSIONS

Then as a first attempt I ran autoconfig on Node 1 "oraapp01" and tried to restart adop again but this time with fs_clone option. This again printed same errors again(pointing to node 2) but luckily it went ahead with fs_clone.

[EVENT]     [START 2015/04/10 22:54:51] Checking the DB parameter value
[EVENT]     [END   2015/04/10 22:54:54] Checking the DB parameter value
    [UNEXPECTED]Unable to find appltop_id for the host oraapp02 from database
    [UNEXPECTED]Unable to find appltop_id for the host oraapp02 from database
 but fs_clone failed at Validation phase and the log file <ADPLOGHOME>/fs_clone_20150410_224816/EBSR12_oraap01/remote_execution_result_20150410_225611.xml showed below details


[ERROR]: Either the value of the context variables_shared_file_system in the run file system is not consistent between the file system and the database or the APPL_TOP name across nodes is not set correctly.

Solution:

This made me think about APPL_TOP Name again. I reviewed my context files on both the application tiers (Primary & Secondary) and found that the context variable s_atName is different on both the nodes.

For a shared Applicaiton Tier APPL_TOP name should be same across all the applicaiton tier nodes.
1) Modified context variable s_atName on Secondary node to Master Application Nodename .
2) Executed autoconfig and bounced services.
3) Then adop is went successfully.