Oracle Database Discussions

A little test:

Suppose 2 different databases (DB1 & DB2) on one server (with one ORACLE_HOME) that has the same account properties for user DB_USER (wich has DBA role)
Suppose the same service name (SRV1) for each database (that was set explicitly in SPFILEs).
Suppose the listener is up and service with name SRV1 has 2 instances (1 for each database).
local listener description is:

LISTENER =
(D E S C R I P T I O N _ L I S T =
( D E S C R I P T I O N =
( A D D R E S S = (P R O T O C O L = T C P )(H O S T = V E G A S )(P O R T = 1 5 2 1 ))
)
)

Suppose local naming method has one connect identifier as

UNKNOWN =
( D E S C R I P T I O N =
( A D D R E S S _ L I S T =
( A D D R E S S = (P R O T O C O L = T C P)(H O S T = V E G A S)(P O R T = 1 5 2 1 )
)
)
(C O N N E C T _ D A T A = (S E R V I C E _ N A M E = S R V 1)
)
)

Note: INSTANCE_NAME is not used in CONNECT_DATA.

Network environment set correctly to reach DB server from client.
All instances is running (DB1 & DB2) and databases are opened and accepted connections
Listener is up on the server.
Service SRV1 is running.

And in SQLPLUS

Enter username: DB_USER@UNKNOWN
Enter password:
...
What would happend?
If client connect successfully which is DB's instance user connected to?


Best regards, Sergey