ORA-12505 error when connecting to databases on the same machine that listen through the same port

I have a database and it's copy in the same machine called DB1 and DB2.

I am trying to connect to both the databases through SQL Developer. I don't have an Oracle Client installed on my windows.

The tnsnames.ORA looks like this:

DB1 =
 (DESCRIPTION = 
   (ADDRESS_LIST =
     (ADDRESS = (PROTOCOL = TCP)(HOST = myserver.com)(PORT = 1521))
   )
 (CONNECT_DATA =
   (SERVICE_NAME = DB1)
 )
)

DB2 =
 (DESCRIPTION = 
   (ADDRESS_LIST =
     (ADDRESS = (PROTOCOL = TCP)(HOST = myserver.com)(PORT = 1521))
   )
 (CONNECT_DATA =
   (SERVICE_NAME = DB2)
 )
)

The listener.ora looks like below:

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = PLSExtPROC)
      (ORACLE_HOME = /product/11.2.0.4/)
      (PROGRAM = extproc)
    )
  )

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1)) 
      (ADDRESS = (PROTOCOL = TCP)(HOST = myserver.com)(PORT = 1521))
    )
  )

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = DB1)
      (SID_NAME = DB1)
      (ORACLE_HOME = /product/11.2.0.4/)
      (PRESPAWN_MAX = 50)
    )
  )

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = DB2)
      (SID_NAME = DB2)
      (ORACLE_HOME = /product/11.2.0.4/)
      (PRESPAWN_MAX = 50)
    )
  )

I am able to connect to DB2 but not to DB1. When I connect to DB1 from SQL Developer I get the ORA-12505 error.

When I run $ ps -ef | grep pmon, I get 2 processes - ora_DB1 and ora_DB2

When I run $ ps -ef | grep tns, I get 1 process - LISTENER

When I run $ lsnrctl status LISTENER, I get the output

Services Summary

Service "DB2" has 1 instance(s). Instance "DB2", status UNKNOWN, has 1 handler(s) for this service...

Why am I unable to connect to "DB1" ?

Solution

Thank all for the help !

It had something to do with dynamic registration. It was set to OFF on the first line of the listener.ora file. Once that was commented out, it was fine. The port remains the same, there was no need to listen through another port.

Also, apparently when I ran the $ lsnrctl status LISTENER, I got the output as status UKNOWN because dynamic registraion was turned OFF.

Service "DB2" has 1 instance(s). Instance "DB2", status UNKNOWN, has 1 handler(s) for this service...

So, 2 databases on the same machine can be configured to listen through the same port.