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Create remote shell
Source environment file
If client application running then
Shutdown client application
Startup client application
Else
Startup client application
Verify client application startup
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For a more detailed discussion and examples please refer to a future MAA best
practices whitepaper on client failover that will be published on the OTN MAA
website.
Create database DB_ROLE_CHANGE trigger
The DB_ROLE_CHANGE trigger is fired whenever the role of the database is
changed. In this step we will create a trigger which will do the following:
Enable the primary specific service name
Update the service name in the LDAP directory to point to the new primary
host
Fast-Start Failover – Oracle Data Guard 10g Release 2 Page 22
Restart middle tiers or client applications
On the primary create the role change trigger. The trigger should at the least start
the primary service name, call ldapmodify to change the net alias in the ldap server,
and calls a script which restarts the middle tier or other client applications:
SQL> create or replace trigger set_rc_svc after
DB_ROLE_CHANGE on database
declare
role varchar(30);
begin
select database_role into role from v$database;
if role = 'PRIMARY' then
DBMS_SERVICE.START_SERVICE('sales');
shell('ldapmodify -D "cn=orcladmin" -w welcome1
-h netfl-labsun1 -p 3061 -v -f
/u01/app/oracle/product/10.2.0/change.ldif');
shell('/u01/app/oracle/product/10.2.0/restart_app');
else
DBMS_SERVICE.STOP_SERVICE('sales');
end if;
end;
If the Data Guard configuration is not using Real Time Apply then archive the
current log to get the changes to the standby database.
SQL> alter system archive log current;
CONCLUSION
Oracle Data Guard has evolved over a number of major Oracle releases into the
most fully functional disaster recovery solution available for the protection of
Oracle data and the high availability of applications that require access to that data
regardless of the nature or scale of events that impact the primary production
system.
Fast-Start Failover further extends Data Guard’s ability to address business
continuity requirements. Fast-Start Failover monitors the Data Guard
configuration 24x7x365 and executes a failover automatically when specific
conditions exist. The automatic nature of Fast-Start Failover avoids delays that
can result from human interaction. Automatic failover is also carefully controlled
so that any risk of data loss or “split brain” processing of transactions is completely
avoided.
“Airbus testing of Data Guard 10g Fast-
Start Failover produced impressive results.
Failover executed in less than a minute.
This was much faster than a cold failover
using third party cluster technology. With
Data Guard, Airbus can achieve continuous
data protection and high levels of
availability using a standard feature of the
Oracle Database .”
—Werner Kawollek
Application Management Operations
Airbus Deutschland GmbH
Fast-Start Failover – Oracle Data Guard 10g Release 2 Page 23
Fast-Start Failover’s automatic reinstatement of the original primary following
failover will in most cases eliminate the time and effort required for a “manual
rebuild” of the original primary database. This makes it easier (and much faster) to
execute failovers rather than incur any downtime while administrators troubleshoot
failures on the primary production system.
New Data Guard 10g Release 2 Role Transition events provide the added
capability to integrate database failover with failover procedures at the middle tier
to quickly and automatically redirect clients and applications to the new primary
database at the standby location – providing an end-to-end solution for achieving
business continuity.
REFERENCES
1. Oracle Data Guard
http://www.oracle.com/technology/deploy/availability/htdocs/DataGuardOverview.html
2. Data Guard Primary Site and Network Best Practices
http://www.oracle.com/technology/deploy/availability/pdf/MAA_DG_NetBestPrac.pdf
3. Oracle Database 10g High Availability Architecture and Best Practices
http://download-west.oracle.com/docs/cd/B14117_01/server.101/b10726/toc.htm
4. Oracle Database 10g Best Practices: Data Guard Redo Apply and Media
Recovery
http://www.oracle.com/technology/deploy/availability/pdf/MAA_WP_10gRecoveryBestPractices.pdf
5. Data Guard SQL Apply Best Practices in Oracle Database 10g
http://www.oracle.com/technology/deploy/availability/pdf/MAA_WP_10gSQLApplyBestPractices.pdf
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