MAA - Oracle 10gR2 Redo Transport and Network Best Practices

Maximum Availability Architecture
value of DB will be implicitly converted to OS prior to the open read only
completing.
If you are unable to open the standby in read-only mode as described above, see
Appendix A for additional instructions that address rare occasions when the
standby database may require additional recovery.
Evaluating if Applications are Suitable for Read-Only Database
An event can be used to validate that a read-only application can be run on an
Active Data Guard standby database. The event will identify any SQL that requires
read-write access to the database. See My Oracle Support Note 1206774.1 for more
information on configuring and using this event. If it is discovered that a reporting
application is not a true read-only application and requires some writes, (a readmostly
application), see Appendix B for additional configuration options using
dblinks.
Application Connection Management
This section contains the following topics:
• Managing Initial Client Connections
• Managing Existing Connections for Unplanned Outages
Managing Initial Client Connections
In steady state, it is important that reporting applications that connect to the
standby database, and primary applications that connect to the primary database,
connect to the database with the correct database role. In addition, following a role
transition, the applications should be able to automatically reconnect to the correct
database. This can be accomplished by having separate service names for the
primary application and reporting application and starting the corresponding
service based on the database role.
In the following example, the primary application is connecting with a service name
of sales_rw and the reporting application is connecting with a service name of
sales_ro. To automate starting and stopping the service, use an “on startup”
trigger that checks the database role and starts the appropriate service.
CREATE OR REPLACE TRIGGER manage_service
after startup on database
DECLARE
role VARCHAR(30);
BEGIN
SELECT DATABASE_ROLE INTO role FROM V$DATABASE;
IF role = 'PRIMARY' THEN
DBMS_SERVICE.START_SERVICE('sales_rw');
ELSE
DBMS_SERVICE.START_SERVICE('sales_ro');
END IF;
END;
Oracle Active Data Guard: Oracle Data Guard 11g Page 10