Oracle DB Shutdown issue

Try this:

COTT3 = 
 (DESCRIPTION =
  (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
  (CONNECT_DATA = 
   (SERVER = DEDICATED)
   (SERVICE_NAME = COTT3)
  )
)

If that doesn't work, replace "SERVICE_NAME" with "SID".

Put this in $ORACLE_HOME/network/admin/listener.ora:

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS_LIST =
        (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
      )
    )
  )

SID_LIST_LISTENER =
(SID_LIST =
    (SID_DESC =
      (SID_NAME = COTT3)
          (ORACLE_HOME = /opt/oracle/oracle/product/10.2.0/db_1 )
    )
  )

Then restart the listener with:

lsnrctl reload

Are you 100% sure that the database has started up?

Does:

ps auxww | grep pmon | grep -i cott3

... produce any output?

Be sure the ORACLE_HOME and ORACLE_SID environment variables are correctly set. Then run sqlplus / AS SYSDBA as a user who is a member of the oradba group on the computer.

Get the machine down forcibly:

SHUTDOWN ABORT

Start it up, but try not to let stuff run wild:

STARTUP RESTRICT

Shut it down more gracefully. Don't stop until recovery is complete.

SHUTDOWN IMMEDIATE

Start it up.

STARTUP