It has been noticed that users that have access granted through OBS units that have many child nodes within them, cannot login to the application. This is being noticed after an upgrade to version 15.9.3 (Patch 3).
The DB was picking a bad execution plan when running the following statement. This is one of many SQL queries that are run against the DB by the application to check the access rights of the user attempting to login.
WHERE USER_ID = :B3
AND OBJECT_ID = :B2
AND PERMISSION_CODE = :B1
AND ROWNUM = 1
A better execution plan was baselined to resolve the issue.