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However, there is a class of applications that are extremely sensitive to downtime.
Critical manufacturing applications where any downtime translates into lost
production, trading systems where downtime results in lost business, online web
retailers where downtime directly effects revenue generation and customer
satisfaction, to name a few. Businesses with such applications cannot tolerate the
additional delay that could result due to a manual process driving the failover. This
delay is compounded if an administrator is not immediately available to execute
failover when needed.
Fast-Start Failover is very well suited for this class of applications. Fast-Start
Failover eliminates the uncertainty of a process that requires manual intervention
and automatically executes a zero data loss failover within seconds of an outage
being detected.
AUTOMATIC CLIENT FAILOVER
There are several approaches to configuring client failover. In each of these
approaches, prior to Fast-Start Failover, accommodations needed to be made for
manual intervention required to execute database failover. Fast-Start Failover
streamlines the process by making database failover automatic. In addition, Data
Guard 10g Release 2 includes a new DB_ROLE_CHANGE [7] system event that
makes it possible to quickly notify clients that a failover has occurred so that they
are automatically redirected to the new primary database. For a more detailed
discussion of automating client failover, please refer to Oracle Data Guard 10g
Release 2 Best Practices for Client Failover [8].
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 24x7 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.
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.
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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 detect Data Guard failovers 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. Oracle Maximum Availability Architecture
http://www.oracle.com/technology/deploy/availability/htdocs/maa.htm
3. Fast-Start Failover: Oracle Data Guard 10g Release 2
http://www.oracle.com/technology/deploy/availability/pdf/MAA_WP_10gR2_FastStartFailove
rBestPractices.pdf
4. Oracle Data Guard Broker (Part #B14230-01)
http://download-west.oracle.com/docs/cd/B19306_01/server.102/b14230/toc.htm
5. Oracle Data Guard 10g Release 2 Switchover and Failover Best Practices
http://www.oracle.com/technology/deploy/availability/pdf/MAA_WP_10gR2_SwitchoverFailo
verBestPractices.pdf
6. Oracle Data Guard Concepts and Administration
http://download-west.oracle.com/docs/cd/B19306_01/server.102/b14239/toc.htm
7. DB_ROLE_CHANGE – Oracle Database Application Developers Guide
http://download-west.oracle.com/docs/cd/B19306_01/appdev.102/b14251/toc.htm
8. Oracle Data Guard 10g Release 2 Best Practices for Client Failover
http://www.oracle.com/technology/deploy/availability/htdocs/maa.htm
A 10gR2 version of this paper will be available soon.
From “Automatic Failover, Data Guard 10g Release 2”
Open World San Francisco, September, 2005
Authors: Joseph Meeks & Mike Smith, Oracle Corporation
Oracle Corporation
World Headquarters
500 Oracle Parkway
Redwood Shores, CA 94065
U.S.A.
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