Oracle 11g Release 2 (11.2 ) New Features : SCAN - Single Client Access Name

Oracle 11g R2 (11.2 ) New Features : SCAN - Single Client Access Name
Virag Sharma

Once you decided to add/remove node from RAC database/cluster. We need to change tns
entry. Oracle 11g R2 introduced new concept called Single Client Access Name (SCAN).
Which eliminate the need to change tnsnetry when nodes are added to or removed from
the Cluster.

RAC Instances register to SCAN listeners as remote listeners. SCAN is fully qulified name.
Oracle recommends to assign 3 address to SCAN , which create three SCAN listeners.

$ srvctl status scan_listener SCAN Listener LISTENER_SCAN1 is enabled SCAN listener LISTENER_SCAN1 is running on node apps001 SCAN Listener LISTENER_SCAN2 is enabled SCAN listener LISTENER_SCAN2 is running on node apps002 SCAN Listener LISTENER_SCAN3 is enabled SCAN listener LISTENER_SCAN3 is running on node apps002

Running following command on Node 2 (apps002)

$ ps -aef |grep -i SCAN oracle 9380 1 0 Aug13 ? 00:01:09 /d01/apps/oracle_crs/11.2/bin/tnslsnr LISTENER_SCAN2 -inherit oracle 9380 1 0 Aug13 ? 00:01:09 /d01/apps/oracle_crs/11.2/bin/tnslsnr LISTENER_SCAN3 -inherit oracle 9993 7114 0 09:57 pts/3 00:00:00 grep -i crs

From above output, it is clear that SCAN listener is running from CRS_HOME

$ srvctl config scan_listener SCAN Listener LISTENER_SCAN1 exists. Port: TCP:1521 SCAN Listener LISTENER_SCAN2 exists. Port: TCP:1521 SCAN Listener LISTENER_SCAN3 exists. Port: TCP:1521 $ srvctl config scan SCAN name: apps-scan, Network: 1/192.168.182.0/255.255.255.0/ SCAN VIP name: scan1, IP: /apps-scan.us.oracle.com/192.168.182.109 SCAN VIP name: scan2, IP: /apps-scan.us.oracle.com/192.168.182.110 SCAN VIP name: scan3, IP: /apps-scan.us.oracle.com/192.168.182.108

tns entry can use single address ( SCAN Name ) in tnsentry , instead os using entry for all Node


tns entry configured to use VIP addresses for Database will work without any issue. using
SCANs is not Medatory ( May be to support backward compatibility )

# # TNS ENTRY with SCAN # test.world = (DESCRIPTION= (ADDRESS=(PROTOCOL=tcp)(HOST==apps-scan.world)(PORT=1521)) (CONNECT_DATA=(SERVICE_NAME=R1211.world)) ) # # TNS Entry without SCAN ( Old way) # test.world = (DESCRIPTION= (ADDRESS_LIST= (ADDRESS=(PROTOCOL=tcp)(HOST=apps001-vip.world)(PORT=1521)) (ADDRESS=(PROTOCOL=tcp)(HOST=apps002-vip.world)(PORT=1521)) ) (CONNECT_DATA=(SERVICE_NAME=R1211.world))) ) )

Clients Can connect to a particular instance of the database using SCAN. Entry will looks like

test.world = (description= (address=(protocol=tcp)(host=apps-scan.world)(port=1521)) (connect_data= (service_name=R1211.world) (instance_name=apps1cl1)))

tns entry configured to use VIP addresses for Database will work without any issue. using

SCANs is not Medatory ( May be to support backward compatibility )

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