Oracle Solution for Error ora-28156

ORA-28156: Proxy user 'string' not authorized to set role 'string' for client 'string'

What triggered the Error:

proxy user has not been granted the right to use a role on behalf of a client.

What should we do to fix it:

ecute the command ALTER USER GRANT CONNECT THROUGH PROXY to grant the needed role.

If this was not sufficient go over to: Oracle Official Support Knowledge Center
Or maybe those geeks at: StackOverflow Board