Release 2 (9.2)
Part Number A96601-01
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| Oracle9i Real Application Clusters Real Application Clusters Guard I - Concepts and Administration Release 2 (9.2) Part Number A96601-01 |
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This chapter describes how to configure the Oracle network for Oracle Real Application Clusters Guard. It contains the following sections:
The following network configurations can be used with Oracle Real Application Clusters Guard:
These options are supported with Oracle Real Application Clusters Guard, but you must configure them according to the guidelines in this chapter. The decision about which type of connection to use depends on the resources available, as well as application and business needs.
Dedicated server environments do not have cross-instance listener registration. A connection request made to a specific instance's listener can be connected only to that instance's service. When the primary instance fails, the re-connection request from the client is rejected by the failed instance's listener. Oracle Real Application Clusters Guard stops the failed instance's listener and the IP address to which it was listening. Oracle Real Application Clusters Guard then restarts the IP address on the node where the secondary instance performs recovery and becomes the primary instance. When the client resubmits the request, the client re-establishes the connection by using the new primary instance's listener that then connects the client to the new primary instance.
Oracle Real Application Clusters Guard uses the LOCAL_LISTENER initialization parameter to specify the network name that resolves to an address of Oracle Net local listeners (listeners that are running on the same machine as the instance). The address is specified in the tnsnames.ora file.
For example, if the LOCAL_LISTENER initialization parameter is set to listener_SALES_HOSTA, and listener_SALES_HOSTA uses TPC/IP on port 1421, then the entry in the tnsnames.ora.ded.pfs file looks like this:
listener_SALES_HOSTA= (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1421))
Suppose an Oracle Real Application Clusters Guard environment called SALES exists as described in the following table.
Configure the LOCAL_LISTENER parameter to allow for service registration. Then the following parameters are defined as shown in the following table.
| Parameter | Node 1 | Node 2 |
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The values of the LOCAL_LISTENER parameter can be resolved through the local tnsnames.ora files on Nodes 1 and 2, respectively:
listener_SALES_HOSTA= (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1421)) listener_SALES_HOSTB= (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1421))
The following actions result from this configuration:
PMON process for instance SALES1 registers with listener SALES_HOSTA_LSNR.
The PMON process for instance SALES2 registers with listener SALES_HOSTB_LSNR.
You can confirm this by asking for a services summary on each node:
LSNRCTL> services SALES_HOSTA_LSNR
You should see output similar to the following:
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1421) Services Summary... Service "sales.oracle.com" has 1 instances. Instance "SALES1" Status: READY Total handlers: 1 Relevant handlers: 1 DEDICATED established:6 refused:0 current:0 max:0 state:ready Session: NS
To get a services summary on HOSTB, enter the following command:
LSNRCTL> services SALES_HOSTB_LSNR
You should see output similar to the following:
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1421) Services Summary... Service "sales.oracle.com" has 1 instances. Instance "SALES2" Status: READY/SECONDARY Total handlers: 1 Relevant handlers: 1 DEDICATED established:11 refused:0 current:0 max:0 state:ready Session: NS
The connect descriptor contains addresses of listeners located on 144.25.28.74 and 144.25.28.75 that listen for connection requests for a database service called SALES.ORACLE.COM with a primary instance role.
The connect descriptor address list features connect-time failover and no client load balancing. Connect-time failover is enabled by setting FAILOVER=ON. When set to ON, the FAILOVER parameter instructs Oracle Net at connect time to fail over to 144.25.28.75 if the first address, 144.215.28.74, fails. The FAILOVER parameter defaults to ON for description lists, descriptions, and address lists.
The SALES_DED net service name enables connections to the instance with the primary instance role. The SERVER=DEDICATED specification forces a dedicated server connection.
Specify the SALES_DED net service name as follows:
SALES_DED= (DESCRIPTION= (LOAD_BALANCE=OFF) (ADDRESS_LIST= (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1421)) (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1421))) (CONNECT_DATA= (SERVICE_NAME=SALES.ORACLE.COM) (SERVER=DEDICATED) (INSTANCE_ROLE=PRIMARY)))
Dynamic service registration relies on the PMON process to register instance information with a listener, as well as the current state and load of the instance and shared server dispatchers. The registered information enables the listener to forward client connection requests to the appropriate service handler.
In Oracle Real Application Clusters Guard, the LISTENER attribute in the DISPATCHER initialization parameter has been configured to allow for dynamic service registration of information to both listeners, also referred to as cross-instance listener registration. The primary instance registers with the primary instance listener as well as the secondary instance listener. This enables the primary instance to accept connections from its local listener, as well as from the secondary instance listener. A secondary instance registers with its local listener as a secondary instance.
Suppose that an Oracle Real Application Clusters Guard environment called SALES exists as described in the following table.
| Environment Component | Node 1 | Node 2 |
|---|---|---|
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Listener |
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Relocatable IP address |
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Define the DISPATCHERS initialization parameter on each node:
DISPATCHERS=
"(ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(LISTENER=listener_SALES)"
DISPATCHERS=
"(ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(LISTENER=listener_SALES)"
The listener value (listener_SALES) can then be resolved through a local tnsnames.ora file on both servers as follows, assuming that the listener alias name is listener_SALES and the two ports are 1526:
listener_SALES=
DESCRIPTION=
(ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1526))
(ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1526))
The following actions result from this configuration:
PMON processes for the SALES1 and SALES2 instances register with both listeners. The listeners are updated dynamically with information about the load of the instances and dispatchers. You can confirm this by asking for a services summary on each node. Enter the following command:
$ lsnrctl
You should see output similar to the following:
LSNRCTL for Solaris: Version 9.0.1.0.0 - Production on 03-JAN-2001 13:54:16 (c) Copyright 2001 Oracle Corporation. All rights reserved. Welcome to LSNRCTL, type "help" for information.
Enter the following command:
LSNRCTL> set display normal
You should see output similar to the following:
Service display mode is NORMAL
Enter the following command:
LSNRCTL> services SALES_HOSTA_LSNR
You should see output similar to the following:
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1526)(QUEUESIZE =1024))) Services Summary... Service "sales.oracle.com" has 2 instances. Instance "sales1" Status: READY Total handlers: 1 Relevant handlers: 1 D000 established:3 refused:0 current:0 max:1022 state:ready (ADDRESS=(PROTOCOL=tcp)(HOST=144.25.28.74)(PORT=60349)) Session: NS Instance "sales2" Status: READY/SECONDARY Total handlers: 1 Relevant handlers: 1 D000 established:0 refused:0 current:0 max:1022 state:ready (ADDRESS=(PROTOCOL=tcp)(HOST=144.25.28.75)(PORT=60858)) Session: NS The command completed successfully
The connect descriptors list specifies connect-time failover and no client load balancing. At connection time, Oracle Net fails over to 144.25.28.75 if the first address, 144.215.28.74, fails.
The SALES_MTS net service name enables connections to the instance with the primary instance role.
If a shared server is specified and a client connection request arrives when no dispatchers are registered, then the request can be handled by a dedicated server process. Oracle Real Application Clusters Guard forces clients to always use a dispatcher because SERVER=SHARED is configured in the connect data portion of the connect descriptor. If a dispatcher is not available, then the client connection request is rejected.
The client connect descriptor uses an address list that contains the listener addresses for the primary instance and the secondary instance. The LOAD_BALANCE parameter is set to OFF because all client connections should go to the primary instance.
For example, define SALES_MTS as follows:
SALES_MTS= (DESCRIPTION=
(LOAD_BALANCE=OFF)
(ADDRESS_LIST=
(ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1526))
(ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1526)))
(CONNECT_DATA=
(SERVICE_NAME=SALES.ORACLE.COM)
(SERVER=SHARED) (INSTANCE_ROLE=PRIMARY)))
Transparent application failover (TAF) instructs Oracle Net to fail over an established connection to a different listener. This enables the user to continue to work, by using the new connection as if the original connection had not failed. Using TAF requires manual configuration of a net service name that includes the FAILOVER_MODE parameter in the CONNECT_DATA portion of the connect descriptor.
This section includes the following topics:
| See Also:
Oracle Net Services Administrator's Guide for more information about TAF |
In this example of a TAF basic dedicated connection, the TAF application first tries to connect to the 144.25.28.74 IP address. If it cannot connect, then it attempts to perform a connect-time failover to 144.25.27.75. If the instance fails after the connection, then the TAF application fails over to the other node's listener, reserving SELECT statements that are in progress. If the failover connection attempt fails, then Oracle Net waits 5 seconds before trying to connect again. Oracle Net attempts to connect up to 180 times.
Specify a TAF basic dedicated connection for the SALES database as follows:
SALES_DED_BASIC= (DESCRIPTION= (LOAD_BALANCE=OFF) (FAILOVER=ON) (ADDRESS_LIST= (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1524)) (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1524))) (CONNECT_DATA= (SERVICE_NAME=SALES.ORACLE.COM) (SERVER=DEDICATED) (INSTANCE_ROLE=PRIMARY) (FAILOVER_MODE= (BACKUP=SALES_DED_BASIC_BACKUP) (TYPE=SELECT) (METHOD=BASIC) (RETRIES=180) (DELAY=5)))) SALES_DED_BASIC_BACKUP= (DESCRIPTION= (LOAD_BALANCE=OFF) (FAILOVER=ON) (ADDRESS_LIST= (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1524)) (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1524))) (CONNECT_DATA= (SERVICE_NAME=SALES.ORACLE.COM) (SERVER=DEDICATED) (INSTANCE_ROLE=PRIMARY) (FAILOVER_MODE= (BACKUP=SALES_DED_BASIC) (TYPE=SELECT) (METHOD=BASIC) (RETRIES=180) (DELAY=5))))
When TAF is configured, a backup connection can be preestablished to the secondary instance. The initial and backup connections are specified explicitly. In the following example, Oracle Net connects to the listener on HOSTA and establishes a preconnection to HOSTB, the secondary instance. If HOSTA fails after the connection, then the TAF application fails over to HOSTB. The RETRIES and DELAY parameters cause Oracle Net to automatically try to connect again if the first connection attempt fails.
In the following example of a TAF preestablished dedicated connection, the TAF application tries to connect to the 144.25.28.74 address first. If it cannot, then Oracle Net attempts connect-time failover to 144.25.27.75. A backup connection is preestablished. If the instance fails after the connection, then the TAF application fails over to the other node's listener, reserving any SELECT statements in progress. If the failover connection attempt fails, then Oracle Net waits 5 seconds before trying to connect again. Oracle Net attempts to connect up to 180 times.
Define a TAF preestablished dedicated connection for the SALES database as follows:
SALES_DED_PRE= (DESCRIPTION= (LOAD_BALANCE=OFF) (FAILOVER=ON) (ADDRESS_LIST= (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1524)) (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1524))) (CONNECT_DATA= (SERVICE_NAME=SALES.ORACLE.COM) (SERVER=DEDICATED) (INSTANCE_ROLE=PRIMARY) (FAILOVER_MODE= (BACKUP=SALES_DED_PRE_SECONDARY) (TYPE=SELECT) (METHOD=PRECONNECT) (RETRIES=180) (DELAY=5)))) SALES_DED_PRE_SECONDARY= (DESCRIPTION= (LOAD_BALANCE=OFF) (FAILOVER=ON) (ADDRESS_LIST= (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.75)(PORT=1524)) (ADDRESS=(PROTOCOL=TCP)(HOST=144.25.28.74)(PORT=1524))) (CONNECT_DATA= (SERVICE_NAME=SALES.ORACLE.COM) (SERVER=DEDICATED) (INSTANCE_ROLE=SECONDARY) (FAILOVER_MODE= (BACKUP=SALES_DED_PRE) (TYPE=SELECT) (METHOD=PRECONNECT) (RETRIES=48) (DELAY=900))))
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