ORA-12203 during 11.5.10.2 maintenance pack

Some of the workers were waiting indefinitely during an 11.5.10.2 upgrade as the DB connection could not be made. The worker error log showed:

Start time for file is: Wed Jul 02 2008 06:49:18

sqlplus -s APPS/***** @$PA_TOP/patch/115/sql/paupg007.sql &un_pa &batchsize 4 48
ERROR:
ORA-12203: TNS:unable to connect to destination


Some of the workers failed with the same error

HIDEPW: $FND_TOP/bin/FNDGFU APPS/TIB5C1US 0 Y PROGRAM_NAME=FND_HELP CONTENT_MAP=@FND:admin/import/fndgfu.txt PROGRAM_TAG
=OKS:10 LANGUAGE=US @OKS:help/US/oks11511084417.htm
$FND_TOP/bin/FNDGFU &ui_apps 0 Y PROGRAM_NAME=FND_HELP CONTENT_MAP=@FND:admin/import/fndgfu.txt PROGRAM_TAG=OKS:10 LANGU
AGE=US @OKS:help/US/oks11511084417.htm
APP-FND-01564: ORACLE error 12203 in AFPCOA

Cause: AFPCOA failed due to ORA-12203: TNS:unable to connect to destination.

The SQL statement being executed at the time of the error was: and was executed
from the file .

AD Worker error:
The above program failed with error code 1.
See the AD Worker log file and/or the program log file for details.


We stopped all workers. Bounced DB listener.

update fnd_install_processes
set status='W', control_code='W';

commit;

Restarted adpatch. It went fine after that.

We are still trying to find the root cause of this issue.