RAC-RAC Enable Steps on Database & Application

To enable RAC on the Application Node follow below steps:

Enabling and Disabling SCAN Listener Support in AutoConfig:

Managing the SCAN listener is handled on the database server.  All that is required for the applications tier is for AutoConfig to be run again to pick up the updated connection strings.

Switching from SCAN to non-SCAN

Modify the database tier context variables s_scan_name=null, s_scan_port=null, and s_update_scan=TRUE.

Modify the database init.ora parameter so that local_listener should be <sid>_local and remote listener <service>_remote [To allow failover aliases].

Run AutoConfig to create the non-SCAN aliases in the tnsnames.ora file.

Run AutoConfig on the application tier to create the non-SCAN aliases in the tnsnames.ora file.

Re-enabling SCAN

Modify the database tier context variables s_scan_name=<scan_name>,s_scan_port=<scan_port>, and s_update_scan=TRUE.

Modify the remote_listener to "<scan_name>:<scan_port>" using alter system set remote_listener='...' for all instances.

Run AutoConfig on the database tier to create SCAN aliases in the tnsnames.ora file.

Run AutoConfig on the application tier to create SCAN aliases in the tnsnames.ora file.

@@@@@@@@@@@@@@ DATABASE @@@@@@@@@@@@@@

NODE 1

Note:

Above for Local Listener enter VIP-NAME for NODE 1

Above for Remote Listener enter scan name.

Above for Scan Name enter scan name without domain name

NODE 2

Note:

Above for Local Listener enter VIP-NAME for NODE 2

Above for Remote Listener enter scan name.

Above for Scan Name enter scan name without domain name

IMP:

Please do not forget to run AUTOCONFIG post changes on respective nodes of the database. 

@@@@@@@@@@@@@@@@@@ APPLICATION @@@@@@@@@@@@@@@@@

Note:

Above for s_dbhost, s_cmanhost, enter scan name.

Enabling and Disabling SCAN Listener Support in AutoConfig

Managing the SCAN listener is handled on the database server.  All that is required for the applications tier is for AutoConfig to be run again to pick up the updated connection strings.

Switching from SCAN to non-SCAN

Modify the database tier context variables s_scan_name=null, s_scan_port=null, and s_update_scan=TRUE.

Modify the database init.ora parameter so that local_listener should be <sid>_local and remote listener <service>_remote [To allow failover aliases].

Run AutoConfig to create the non-SCAN aliases in the tnsnames.ora file.

Run AutoConfig on the application tier to create the non-SCAN aliases in the tnsnames.ora file.

Re-enabling SCAN

Modify the database tier context variables s_scan_name=<scan_name>,s_scan_port=<scan_port>, and s_update_scan=TRUE.

Modify the remote_listener to "<scan_name>:<scan_port>" using alter system set remote_listener='...' for all instances.

Run AutoConfig on the database tier to create SCAN aliases in the tnsnames.ora file.

Run AutoConfig on the application tier to create SCAN aliases in the tnsnames.ora file.

Instance and Listener Interaction:

Understanding how instances and listeners interact is best explained with an example.

Consider a 2-node Oracle RAC cluster, with nodes C1 and C2.

In this example, two local listeners are used, the default listener and an EBS listener.  There is nothing special about the EBS listener - it could equally have been called the ABC listener.

Listener Configuration

Listener Type	Node	SCAN Name	Host Name	VIP Name	Listener Host	Listener Port	Listener Address
EBS listener	C1	N/A	C1	C1-VIP	C1	1531	C1 and C1-VIP
	C2	N/A	C2	C2-VIP	C2	1531	C2 and C2-VIP
Default listener	C1	N/A	C1	C1-VIP	C1	1521	C1 and C1-VIP
	C2	N/A	C2	C2-VIP	C2	1521	C2 and C2-VIP
SCAN	Either C1 or C2	C-SCAN	N/A	N/A	Either C1 or C2	1521	C-SCAN

Note the following:

• The SCAN and local listeners can use the same port as they listen on different addresses.
• The SCAN listener can run on either C1 or C2.
• Listeners have no intrinsic relationship to specific instances.

SRVCTL configuration

Listener Type	Listener Name	Listener Port	Listener Host	Listener Address
General [Local]	listener	1521	C1	C1 and C1-VIP
		1521	C2	C2 and C2-VIP
	ebs_listener	1531	C1	C1 and C1-VIP
		1531	C2	C2 and C2-VIP
SCAN	SCAN [ name doesn't matter and can be default ]	1521	Either C1 or C2	C-SCAN

Instance to Listener Assignment

The relationship between instances and listeners is established by the local_listener and remote_listener init.ora parameters (or spfile):

Local_Listener

• The instance broadcasts to the address list, informing the listeners that the instance is now available. The local listener must be running on the same node as the instance, as the listener spawns the Oracle processes. The default value comes from the cluster.
  

Remote_Listener

• The instances broadcast to the address list, informing the listeners that the instance is now available to accept requests, and that the requests are to be handled by the local_listener address. The remote hosts can be on any machine. There is no default value for this parameter.

Database	Instance	Node	Local_Listener	Remote_Listener	Default Listener Status	EBS Listener Status	SCAN Listener Status
D1	I1	C1	Set to C1 & C1-VIP on 1531	C-SCAN/1521	I1 is unavailable	I1 is available	I1 is available via redirect to EBS Listener for C1
			Set to C1 & C1-VIP on 1531	C1/C1-VIP on 1531, C2/C2-VIP on 1531	I1& I2 are unavailable	I1 is available. I2 is available via redirect to EBS Listener for C2.	I1 not available
			Not set.  Instance uses cluster default listener - i.e. C1 & C1-VIP on 1521	C-SCAN/1521	I1 is available	I1 is unavailable.	I1 is available via redirect to Default Listener for C1
	I2	C2	Set to C2 & C2-VIP on 1531	C-SCAN/1521	I2 is unavailable	I2 is available	I2 is available via redirect to EBS Listener for C2
			Set to C2 & C2-VIP on 1531	C1/C1-VIP on 1531, C2/C2-VIP on 1531	I2 & I1 are unavailable	I2 is available. I1 is available via redirect to EBS Listener for C1.	I2 not available
			Not set.  Instance uses cluster default listener - i.e. C2 & C2-VIP on 1521	C-SCAN/1521	I2 is available	I2 is unavailable	I2 is available via redirect to Default Listener for C2

Reference:

Using Oracle 12c Release 1 Real Application Clusters with Oracle E-Business Suite Release 12 (Doc ID 1490850.1)