In 11gR2, Oracle introduced a new feature called Single Client Access Name (SCAN). This new feature created a lot of confusions to me, so I decided to do some research to under this new feature.
I found following Oracle Support notes and other online sources explaining this new feature
1 11gR2 Grid Infrastructure Single Client Access Name (SCAN) Explained [ID 887522.1]
1.1 SCAN Concepts
1.2 Common Questions Regarding SCAN
1.2.1 How can we configure the SCAN and SCAN listener?
1.2.2 Do we still need to configure local listeners on each node?
1.2.3 How does SCAN work ?
1.2.4 Instead of DNS or GNS, Can we use '/etc/hosts' to resolve SCAN?
1.2.5 Can we use the previous method (Using VIP) for client connection?
1.2.6 Is it mandatory to use SCAN?
1.2.7 Is it supported to remove SCAN?
1.2.8 Demo
1.3 References
NOTE:1053147.1 - 11gR2 Clusterware and Grid Home - What You Need to Know
NOTE:887471.1 - PRVF-4664 PRVF-4657: Found inconsistent name resolution entries for SCAN name
NOTE:972500.1 - How to Modify SCAN Setting after Installation
NOTE:975457.1 - How to Troubleshoot Connectivity Issue with 11gR2 SCAN Name
11.2 Scan and Node TNS Listener Setup Examples [ID 1070607.1]
Real Application Clusters Admin and Deployment Guide
Clusterware Administration and Deployment Guide
Oracle Grid Infrastructure Installation Guide
www.oracle.com/technetwork/database/clustering/overview/scan-129069.pdf
2 How to set up SCAN? How to check SCAN status?
2.1 First of all, verify SCAN VIP and Listener setup
[oracle@racdbdb01 admin]$ $GRID_HOME/bin/cluvfy comp scan -verbose
Verifying scan
Checking Single Client Access Name (SCAN)...
SCAN Name Node Running? ListenerName Port Running?
---------------- ------------ ------------ ------------ ------------ ------------
racdb-scan racdbdb02 true LISTENER_SCAN1 1521 true
racdb-scan racdbdb01 true LISTENER_SCAN2 1521 true
racdb-scan racdbdb01 true LISTENER_SCAN3 1521 true
Checking TCP connectivity to SCAN Listeners...
Node ListenerName TCP connectivity?
------------ ------------------------ ------------------------
localnode LISTENER_SCAN1 yes
localnode LISTENER_SCAN2 yes
localnode LISTENER_SCAN3 yes
TCP connectivity to SCAN Listeners exists on all cluster nodes
Checking name resolution setup for "racdb-scan"...
SCAN Name IP Address Status Comment
------------ ------------------------ ------------------------ ----------
racdb-scan 192.168.100.174 passed
racdb-scan 192.168.100.175 passed
racdb-scan 192.168.100.176 passed
Verification of SCAN VIP and Listener setup passed
Verification of scan was successful.
Note: in my environment, before the RAC installation, our SA had decided which IPs to be used for SCAN IPs, and set it up in DNS. During RAC installation, it prompted for the SCAN name.
2.2 check /etc/hosts file to see if IPs used by SCAN are set.
2.3 check DNS setup for the scan address
[oracle@racdb01 admin]$ nslookup rac-scan
Server: 192.168.100.10
Address: 192.168.100.10#53
Name: rac-scan.hostdb.com
Address: 192.168.100.174
Name: rac-scan.hostdb.com
Address: 192.168.100.176
Name: rac-scan.hostdb.com
Address: 192.168.100.175
2.4 Differences between SCAN Listener and Node Listener
-- Oracle recommends using 3 SCAN listeners for RAC. If the RAC has 3 nodes, each node will have its own SCAN listener. If there is only 1 SCAN listener configured, then only 1 node would have the SCAN Listener running.
-- Each node has its own listener, just like the regular listener in the single instance database.
-- Warning: make sure that both SCAN Listener and Node (Local) Listener are running from the $GRID_HOME, not the one from the $ORACLE_HOME
[oracle@racdb01 admin]$ ps -ef |grep tnslsnr
oracle 11778 1 0 Feb16 ? 00:00:55 /u01/app/11.2.0/grid/bin/tnslsnr LISTENER_SCAN3 -inherit
oracle 11780 1 0 Feb16 ? 00:00:54 /u01/app/11.2.0/grid/bin/tnslsnr LISTENER_SCAN2 -inherit
oracle 11783 1 0 Feb16 ? 00:01:04 /u01/app/11.2.0/grid/bin/tnslsnr LISTENER -inherit
=======================================================
[oracle@node1 ~]$ ps -ef |grep tnslsnr
oracle 15702 1 0 Jan18 ? 00:14:55 /u01/11.2.0.2/grid/bin/tnslsnr LISTENER_SCAN1 -inherit
oracle 16015 1 0 Jan18 ? 00:15:43 /u01/11.2.0.2/grid/bin/tnslsnr LISTENER -inherit
oracle 21481 1293 0 15:10 pts/0 00:00:00 grep tnslsnr
Note:
1 racdb01 is part of 2 nodes cluster with 3 SCAN Listener configured, so 2 SCAN Listener are running from the same node. racdb02 has only 1 SCAN listener running.
2 node1 is part of 2 nodes cluster with only 1 SCAN Listener configured.
2.5 LOCAL_LISTENER vs REMOTE_LISTENER
-- Database parameter LOCAL_LISTENER points to Node VIP address
SQL> show parameter local_listener
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
local_listener string (DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=racdb01-vip)(PORT=1521))))
--Database Parameter REMOTE_LISTENER points to SCAN name
SQL> show parameter remote_listener
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
remote_listener string rac-scan.hostdb.com:1521
Note: please pay extra attention to these two listener settings. In 10g, if these 2 are not set correctly, TAF would not work properly.
2.6 listener.ora file
Warning: make sure it's the $GRID_HOME/network/admin/listener.ora being used by the database.
[oracle@racdb01 admin]$ cat $GRID_HOME/network/admin/listener.ora
LISTENER=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER)))) # line added by Agent
LISTENER_SCAN3=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN3)))) # line added by Agent
LISTENER_SCAN2=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN2)))) # line added by Agent
LISTENER_SCAN1=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))) # line added by Agent
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER_SCAN1=ON # line added by Agent
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER_SCAN2=ON # line added by Agent
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER_SCAN3=ON # line added by Agent
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER=ON # line added by Agent
ADMIN_RESTRICTION_LISTENER=ON
SQLNET.EXPIRE_TIME=10
=======================================================
[oracle@node1 ~]$ cat $GRID_HOME/grid/network/admin/listener.ora
LISTENER=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER)))) # line added by Agent
LISTENER_SCAN1=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))) # line added by Agent
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER_SCAN1=ON # line added by Agent
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER=ON # line added by Agent
Note: The ENABLE_GLOBAL_DYNAMIC_ENDPOINT_ parameter is set to allow the listener to accept connections for pre-11.2 databases which did not register the dynamic endpoint.
2.7 Listener status checking:
Before check node listener and SCAN listener status, make sure set TNS_ADMIN=$GRID_HOME/network/admin.
-- lsnrctl status listener
The above command would show 1 instance registered, which is the local instance running on the node where the above command is executed.
[oracle@racdb01 admin]$ lsnrctl status listener
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 01-APR-2011 15:25:06
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.2.0 - Production
Start Date 16-FEB-2011 16:09:37
Uptime 43 days 22 hr. 15 min. 29 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/app/11.2.0/grid/network/admin/listener.ora
Listener Log File /u01/app/oracle/diag/tnslsnr/racdb01/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.100.172)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.250.10)(PORT=1521)))
Services Summary...
Service "+ASM" has 1 instance(s).
Instance "+ASM1", status READY, has 1 handler(s) for this service...
Service "rac" has 1 instance(s).
Instance "rac1", status READY, has 1 handler(s) for this service...
Service "rac_taf" has 1 instance(s).
Instance "rac1", status READY, has 1 handler(s) for this service...
The command completed successfully
=======================================================
[oracle@node1 ~]$ lsnrctl status listener
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 01-APR-2011 15:25:00
Copyright (c) 1991, 2009, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=node1.hostdb.com)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.2.0 - Production
Start Date 18-JAN-2011 16:54:26
Uptime 72 days 21 hr. 30 min. 33 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/11.2.0.2/grid/network/admin/listener.ora
Listener Log File /u02/oracle/diag/tnslsnr/node1/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.100.130)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.100.211)(PORT=1521)))
Services Summary...
Service "netapp_taf.hostdb.com" has 1 instance(s).
Instance "racflo1", status READY, has 1 handler(s) for this service...
Service "racflo.hostdb.com" has 1 instance(s).
Instance "racflo1", status READY, has 1 handler(s) for this service...
Service "racfloXDB.hostdb.com" has 1 instance(s).
Instance "racflo1", status READY, has 1 handler(s) for this service...
The command completed successfully
2.8 endpoints_listener.ora
"New file for 11.2 called endpoints_listener.ora, showing the Node IP address and Node VIP address."
[grid@netrac1 admin]$ more endpoints_listener.ora
LISTENER_NETRAC1=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=netrac1-vip)(PORT=1521))(ADDRESS=(PROTOCOL=TCP)(HOST=12.345.678.888)(PORT=1521)(IP=FIRST)))) # line added by Agent
"
Endpoints_listener.ora file is there for backward compatibility with pre-11.2 databases.
DBCA needs to know the endpoints location to configure database parameters and tnsnames.ora file.
It used to use the listener.ora file, 11.2 RAC listener.ora by default only has IPC entries."
2.9 Check SCAN Listener status
Warning: before check node listener and SCAN listener status, make sure set TNS_ADMIN=$GRID_HOME/network/admin.
-- In my 1st set of cluster, only one SCAN listener configured, so in node1:
[oracle@node1 ~]$ lsnrctl status listener_scan1
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 01-APR-2011 15:32:35
Copyright (c) 1991, 2009, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))
STATUS of the LISTENER
------------------------
Alias LISTENER_SCAN1
Version TNSLSNR for Linux: Version 11.2.0.2.0 - Production
Start Date 18-JAN-2011 16:53:06
Uptime 72 days 21 hr. 39 min. 29 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/11.2.0.2/grid/network/admin/listener.ora
Listener Log File /u01/11.2.0.2/grid/log/diag/tnslsnr/node1/listener_scan1/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER_SCAN1)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.100.210)(PORT=1521)))
Services Summary...
Service "netapp_taf.hostdb.com" has 2 instance(s).
Instance "racflo1", status READY, has 1 handler(s) for this service...
Instance "racflo2", status READY, has 1 handler(s) for this service...
Service "racflo.hostdb.com" has 2 instance(s).
Instance "racflo1", status READY, has 1 handler(s) for this service...
Instance "racflo2", status READY, has 1 handler(s) for this service...
Service "racfloXDB.hostdb.com" has 2 instance(s).
Instance "racflo1", status READY, has 1 handler(s) for this service...
Instance "racflo2", status READY, has 1 handler(s) for this service...
The command completed successfully
======================
In node2, there is no SCAN listener running:
[oracle@node2 ~]$ ps -ef |grep tnslsnr
oracle 14517 1 0 Jan18 ? 00:14:05 /u01/11.2.0.2/grid/bin/tnslsnr LISTENER -inherit
oracle 15673 15301 0 15:36 pts/0 00:00:00 grep tnslsnr
============================================
In my 2nd set of 2 nodes cluster, 3 SCAN listener were configured, so in the 1st node:
[oracle@racdb01 ~]$ ps -ef |grep tnslsnr
oracle 11778 1 0 Feb16 ? 00:00:55 /u01/app/11.2.0/grid/bin/tnslsnr LISTENER_SCAN3 -inherit
oracle 11780 1 0 Feb16 ? 00:00:54 /u01/app/11.2.0/grid/bin/tnslsnr LISTENER_SCAN2 -inherit
oracle 11783 1 0 Feb16 ? 00:01:05 /u01/app/11.2.0/grid/bin/tnslsnr LISTENER -inherit
oracle 18197 30756 0 15:44 pts/0 00:00:00 grep tnslsnr
[oracle@racdb01 ~]$ export TNS_ADMIN=$GRID_HOME/network/admin
[oracle@racdb01 ~]$ lsnrctl status listener_scan1
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 01-APR-2011 15:44:51
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
TNS-00511: No listener
Linux Error: 2: No such file or directory
[oracle@racdb01 ~]$ lsnrctl status listener_scan2
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 01-APR-2011 15:44:53
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN2)))
STATUS of the LISTENER
------------------------
Alias LISTENER_SCAN2
Version TNSLSNR for Linux: Version 11.2.0.2.0 - Production
Start Date 16-FEB-2011 16:09:37
Uptime 43 days 22 hr. 35 min. 15 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/app/11.2.0/grid/network/admin/listener.ora
Listener Log File /u01/app/11.2.0/grid/log/diag/tnslsnr/racdb01/listener_scan2/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER_SCAN2)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.100.174)(PORT=1521)))
Services Summary...
Service "racdb" has 2 instance(s).
Instance "racdb1", status READY, has 1 handler(s) for this service...
Instance "racdb2", status READY, has 1 handler(s) for this service...
Service "racdb_taf" has 2 instance(s).
Instance "racdb1", status READY, has 1 handler(s) for this service...
Instance "racdb2", status READY, has 1 handler(s) for this service...
The command completed successfully
[oracle@racdb01 ~]$ lsnrctl status listener_scan3
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 01-APR-2011 15:44:55
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN3)))
STATUS of the LISTENER
------------------------
Alias LISTENER_SCAN3
Version TNSLSNR for Linux: Version 11.2.0.2.0 - Production
Start Date 16-FEB-2011 16:09:37
Uptime 43 days 22 hr. 35 min. 17 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/app/11.2.0/grid/network/admin/listener.ora
Listener Log File /u01/app/11.2.0/grid/log/diag/tnslsnr/racdb01/listener_scan3/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER_SCAN3)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.100.175)(PORT=1521)))
Services Summary...
Service "racdb" has 2 instance(s).
Instance "racdb1", status READY, has 1 handler(s) for this service...
Instance "racdb2", status READY, has 1 handler(s) for this service...
Service "racdb_taf" has 2 instance(s).
Instance "racdb1", status READY, has 1 handler(s) for this service...
Instance "racdb2", status READY, has 1 handler(s) for this service...
The command completed successfully
[oracle@racdb01 ~]$
In the 2nd node:
[oracle@racdb02 ~]$ ps -ef |grep tnslsnr
oracle 12312 12101 0 15:47 pts/0 00:00:00 grep tnslsnr
oracle 13398 1 0 Feb16 ? 00:00:35 /u01/app/11.2.0/grid/bin/tnslsnr LISTENER -inherit
oracle 13558 1 0 Feb16 ? 00:00:48 /u01/app/11.2.0/grid/bin/tnslsnr LISTENER_SCAN1 -inherit
[oracle@racdb02 ~]$ lsnrctl status listener_scan1
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 01-APR-2011 15:48:10
Copyright (c) 1991, 2010, Oracle. All rights reserved.
TNS-01101: Could not find service name listener_scan1
[oracle@racdb02 ~]$ lsnrctl status listener_scan2
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 01-APR-2011 15:48:20
Copyright (c) 1991, 2010, Oracle. All rights reserved.
TNS-01101: Could not find service name listener_scan2
[oracle@racdb02 ~]$ export TNS_ADMIN=$GRID_HOME/network/admin
[oracle@racdb02 ~]$ lsnrctl status listener_scan1
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 01-APR-2011 15:48:26
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))
STATUS of the LISTENER
------------------------
Alias LISTENER_SCAN1
Version TNSLSNR for Linux: Version 11.2.0.2.0 - Production
Start Date 16-FEB-2011 16:10:01
Uptime 43 days 22 hr. 38 min. 25 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/app/11.2.0/grid/network/admin/listener.ora
Listener Log File /u01/app/11.2.0/grid/log/diag/tnslsnr/racdb02/listener_scan1/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER_SCAN1)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.100.176)(PORT=1521)))
Services Summary...
Service "rac" has 2 instance(s).
Instance "rac1", status READY, has 1 handler(s) for this service...
Instance "rac2", status READY, has 1 handler(s) for this service...
Service "rac_taf" has 2 instance(s).
Instance "rac1", status READY, has 1 handler(s) for this service...
Instance "rac2", status READY, has 1 handler(s) for this service...
The command completed successfully
[oracle@racdb02 ~]$ lsnrctl status listener_scan2
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 01-APR-2011 15:48:31
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN2)))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
TNS-00511: No listener
Linux Error: 2: No such file or directory
2.10 Further information on the listeners can be found via svrctl.
Configuration changes to the Listener are made via svrctl.
[oracle@racdb02 ~]$ 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
[oracle@racdb02 ~]$ srvctl config scan
SCAN name: rac-scan, Network: 1/192.168.100.0/255.255.255.0/bondeth0
SCAN VIP name: scan1, IP: /rac-scan.hostdb.com/192.168.100.176
SCAN VIP name: scan2, IP: /rac-scan.hostdb.com/192.168.100.174
SCAN VIP name: scan3, IP: /rac-scan.hostdb.com/192.168.100.175
[oracle@node1 ~]$ srvctl config scan
SCAN name: rac-cluster.hostdb.com, Network: 1/192.168.100.0/255.255.255.0/bond0
SCAN VIP name: scan1, IP: /rac-cluster.hostdb.com/192.168.100.210
[oracle@node1 ~]$ srvctl config scan_listener
SCAN Listener LISTENER_SCAN1 exists. Port: TCP:1521
3 References
- How To Configure Server Side Transparent Application Failover [ID 460982.1]
- Note 952903.1 How to update the IP address of the SCAN VIP resources (ora.scan.vip)
- Note 975457.1 How to Troubleshoot Connectivity Issue with 11gR2 SCAN Name
- Note 972500.1 How to Modify SCAN Setting after Installation
- NOTE:948456.1 - Pre 11.2 Database Issues in 11gR2 Grid Infrastructure Environment
- How to Access a RAC Database configured with SCAN via Java Thin Driver [ID 1081179.1]
- How to Setup SCAN Listener and Client for TAF and Load Balancing [Video] [ID 1188736.1]
- ORA-12545 or ORA-12537 Reported while Connecting to RAC through SCAN name [ID 970619.1]
Labels: 11gR2, RAC, SCAN