AccessGate Login Fails with HTTP 500 Error after ADOP Cycle

I was facing the subject problem after successful ADOP cycle, Single Sign On SSO does not work and throws HTTP 500 Error at login.
Below shows that ADOP cycle was successful,

But when we try to access the application we get below error,

EBS 12.2 AccessGate Login Fails with HTTP 500 Error 'Request Failed for : /accessgate/ssologin?, Resp Code : [500]' On Secondary Nodes After A Complete ADOP Patching Cycle As File oaea_wls.properties is Not Updated On Multiple Filesystems (fs2)

In some cases fs_clone can fail to copy the file oaea_wls.properties to the other filesystem fs2 for the additional apps nodes.
For example, on the secondary apps tiers using a different filesystem (fs2), file oaea_wls.properties will have null settings for some parameters:
# +======================================================================+
# |    Copyright (c) 2005, 2014 Oracle and/or its affiliates.           |
# |                         All rights reserved.                         |
# |                           Version 12.0.0                             |
# +======================================================================+
# $Header: oaea_wls_properties.tmp 120.0.12020000.1 2014/07/15 12:36:37 mmanku noship $
#
# This file lists all the  parameters required to start acessgate application
# /u03/eruat/fs1/EBSapps/appl/fnd/12.0.0
# ###############################################################
#
# Do not edit settings in this file manually. They are managed
# automatically and will be overwritten when AutoConfig runs.
# For more information about AutoConfig, refer to the Oracle
# E-Business Suite Setup Guide.
#
# ###############################################################
SSO_SERVER_RELEASE=
SSO_SERVER_URL=
SSO_SERVER_TYPE=
LOG_CONFIG_FILE=DEFAULT
APPL_SERVER_ID=
OAM_LOGOUT_URL=
CONNECTION_REF=
WEBGATE_LOGOUT=
oracle.apps.fnd.sso.WebEntries=DEFAULT
In certain cases for an ONLINE patching cycle, the file $INST_TOP/appl/admin/oaea_wls.properties does not get copied from RUN to PATCH.
The issue is documented in the following unpublished defect:
Bug 25720619 - ERROR 500 INTERNAL SERVER ERROR TRYING TO LOGIN AFTER PATCH CYCLE
Workaround Fix:
To resolve the issue test the following steps in a development instance and then migrate accordingly:
1. Ensure a valid backup exists for the instance where the solution is being testing.
2. Copy file $INST_TOP/appl/admin/oaea_wls.properties from the original filesystem (fs1) over to the additional filesystems (fs2), to migrate the proper node settings to oaea_wls.properties
3. Restart the servers to ensure the file changes are processed.
4. Retest the login and confirm the error is resolved.
Following should be the content of the file oaea_wls.properties

This is the latest update as of 28-August-2017 for this issue, there is a patch for this defect 25720619 that is planned to be released in the next AD / TXK Delta patchset, with no release date information currently available.

For any queries on this article, kindly email me samiappsdba@gmail.com