Wednesday, September 2, 2009

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

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 )

More Post on Oracle RDBMS Database 11g R2 ( Release 2 ) 

Oracle 11g Release 2 (11.2 ) New Features : SCAN - Single Client Access Name
11G R2 New Feature : Purge audit trail records using DBMS_AUDIT_MGMT
Oracle Database 11g Release 2 New Features : Edition based redefination

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