Technical Considerations for a Serviceguard Cluster that Spans Multiple IP Subnets, July 2009

To automatically reconnect clients to the database after a cross-subnet failover, the Oracle Net service

names (e.g.: rac1vip1 – rac2vip2) must include VIPs configured at both sub-clusters. Figure 10

shows a sample tnsnames.ora file.

Figure 10 – Example tnsnames.ora configuration file for an Oracle RAC database with 2 nodes at each site and dedicated

protocol address entries

DB_RAC =

(DESCRIPTION =

(ADDRESS_LIST=

(FAILOVER = on)

(LOAD_BALANCE = on)

(ADDRESS = (PROTOCOL = TCP)(HOST = rac1vip1.hp.com)(PORT = 1521))

(ADDRESS = (PROTOCOL = TCP)(HOST = rac1vip2.hp.com)(PORT = 1521))

(ADDRESS = (PROTOCOL = TCP)(HOST = rac2vip1.hp.com)(PORT = 1521))

(ADDRESS = (PROTOCOL = TCP)(HOST = rac2vip2.hp.com)(PORT = 1521))

)

(CONNECT_DATA=

(SERVICE_NAME = DB_RAC)

)

For more detailed information on Oracle net service configuration, please see the Oracle® Database

Net Services Reference manual at:

http://download.oracle.com/docs/cd/B19306_01/network.102/b14213.pdf.

The information about CTF, TAF, and the SQLNET.OUTBOUND_CONNECT_TIMEOUT parameter

provided in the “Client access to a single instance Oracle database” section also applies to clients

connecting to an Oracle RAC database.

While TAF requires the client to be OCI compliant, JDBC clients can make use of Fast Connection

Failover (FCF), sometimes also called Fast Application Failover (FAF), if they make use of the JDBC

implicit connection pool.

Fast Application Notification (FAN)

Fast Application Notification is a notification mechanism that Oracle introduced with 10g to notify

other processes about configuration and service-level information, including status changes such as UP

or DOWN events for Oracle instances, services, and nodes. Oracle Notification Services (ONS)

needs to be configured among all systems – cluster nodes and systems running client applications to

be able to subscribe to FAN events.

ONS is setup automatically among the cluster nodes during the Oracle RAC installation. Since a

SADTA SGeRAC Metrocluster consists of two Oracle sub-clusters, the nodes of sub-cluster A need to

be added manually to the ONS configuration of the nodes from sub-cluster B and vice versa. For

Oracle cluster nodes, this is achieved by:

racgons add_config hostname:port [hostname:port] …

This updates the information in the Oracle cluster registry. For single instance database nodes and

systems that run Oracle client applications, the ONS configuration needs to be done manually by

adding entries for each system in the ONS configuration file on every system. This example shows

sample ONS configuration file for a client system accessing a RAC database matching the description

of Figure 10:

# This is an example ons.config file

localport=4100