Oracle Listner and tnsnames related query

Question

Hi ,
DB verison 10.2.0.1.0.
i have 3 databases running on my machine.
(Listner entry)
# listener.ora Network Configuration File: D:\oracle_2\network\admin\listener.ora
# Generated by Oracle configuration tools.
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = D:\oracle_2)
(PROGRAM = extproc)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.180.1)(PORT = 1521))
(Tnsnames entry)
# tnsnames.ora Network Configuration File: D:\oracle_2\NETWORK\ADMIN\tnsnames.ora
# Generated by Oracle configuration tools.
DEV =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.180.1)(PORT = 1521))
(CONNECT_DATA =
(SERVER = SHARED)
(SERVICE_NAME = DEV)
CPDB =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.180.1)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = cpdb)
ORCL =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.180.1)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = orcl)
EXTPROC_CONNECTION_DATA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
(CONNECT_DATA =
(SID = PLSExtProc)
(PRESENTATION = RO)
My query is as follows.
i have DEV,ORCL,CPDB db names on my local machine.service name is same as db_name.
for DEV tnsnames entry is
DEV =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.180.1)(PORT = 1521))
(CONNECT_DATA =
(SERVER = SHARED)
(SERVICE_NAME = DEV)
when a client want to connect to DEV database ,above entry will be configured in tnsnames.ora and services name DEV can be used at client side.
Now when actully connection get established first protocl TCP is used for communication,then 192.168.180.1 is find out then port 1521 is used.
Now my question is how that establishing connection knows to connect to which database if there are more database on same host ? is that again tnsnames.ora parameter SERVICE_NAME = DEV indicate as db_name to get connect on db server?

Answer 1

Below is the ex how we do it in real time environment. If 2 databases Test,Stage running on same server then we configure different listener to listen each database.
Stage listener.ora :
==================
Stage =
(ADDRESS_LIST =
(ADDRESS= (PROTOCOL= IPC)(KEY= EXTPROCStage))
(ADDRESS= (PROTOCOL= TCP)(Host= Server06.oracleoutsourcing.com )(Port= 10910))
Test listener.ora :
==================
Test =
(ADDRESS_LIST =
(ADDRESS= (PROTOCOL= IPC)(KEY= EXTPROCTest))
(ADDRESS= (PROTOCOL= TCP)(Host= Server06.oracleoutsourcing.com )(Port= 10710))
tnsnames.ora for client :
========================
Stage=
(DESCRIPTION=
(ADDRESS=(PROTOCOL=tcp)(HOST=Server06.oracleoutsourcing.com)(PORT=10910))
(CONNECT_DATA=
(SID=Stage)
Test=
(DESCRIPTION=
(ADDRESS=(PROTOCOL=tcp)(HOST=Server06.oracleoutsourcing.com)(PORT=10710))
(CONNECT_DATA=
(SID=Test)
)