Capture Login Of Terminal In Audit Trail When Login Through Grid?

I am trying to understand how to enable some audit so we can capture OEM logins as well.

Here is my setup. Lets say my DB that i am auditing is called audit_db (audit trail set to DB) sitting on host called host_db. and we have grid control agent on this box.now my grid control is as this. Lets say my OMS and repository is on host called OMS_host.

we run query aginst dba_audit_session to get info as to who tried failed login attemps and stuff.

Now to the part that is not working.

-- this is the good part When i intentionaly login to the audit_db with sqlplus client from my laptop with wrong username/password that is captured. we get the username,os_username,userhost,terminal.

here is the sample output

username is the wrong user that i tried to login as
os_username is the my local username(ad account)
userhost is my_laptop_name
terminal is laptop_name

from above we can figure who was trying to login(failed).

-- this is the bad part But lets say i try to login to audit_db through grid control and use wrong username/password.that gets captured too(but not all of it). we get the username,os_username,userhost,terminal.

here is the sample output

username is the wrong user that i tried to login as
os_username is the user of OMS repository db(oracle)
userhost is oms_host
terminal is unknown

Now with the above info, we cannot figure out who tried to login with bad login credential.