SCAN Listener

SCAN Listener

New Feature in Oracle 11g

Single Client Access Name (SCAN) allows clients to use one name in connection string to connect to the cluster as a whole.  

Why SCAN listener?

1. Removes the requirements to change the client connect if cluster changes were made

2. Load Balance across the instance providing a service

3. Failover between moved instance

Note: REMOTE_LISTERNER register the instance with all SCAN listeners.

 

How to Configure SCAN listener in RAC?

# Prerequite

the SCAN name with three ip addresses assigned via DNS in round robin fashion

# Configure

In the step 4 of 16 of Oracle Grid Instrastructure/Install and Configure Grid Infrastructure of a grid

# listener.ora

LISTENER=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER))))

   

LISTENER_SCAN1=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))) 

LISTENER_SCAN2=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN2)))) 

LISTENER_SCAN3=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN3)))) 

ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER_SCAN1=ON      
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER_SCAN2=ON      
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER_SCAN3=ON          

ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER=ON                     

# endpoints_listener.ora
   LISTENER_LNX200=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=lnx200-vip)(PORT=1521))(ADDRESS=(PROTOCOL=TCP)(HOST=10.10.10.10)(PORT=1521)(IP=FIRST))))           # line added by Agent

# tnsnames.ora

ORCL =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = ORACL01.com)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl)
    )
  )

# start/stop sequence

srvctl start listener

srvctl start scan

srvctl start scan_listener

stop in the same order as above

# How to check config

srvctl config  listener

srvctl config  scan

srvctl config  scan_listener

# How to check status

srvctl status listener

srvctl status scan

srvctl status scan_listener