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  Oracle Database Rolling Upgrade Using Data Guard SQL Apply - (10g to 11g) — (01-June-2012)

An Oracle rolling database upgrade eliminates lengthy downtime associated with 
the conventional database upgrade and can also provide an efficient fail back 
method in case of an emergency during the upgrade. A rolling upgrade also 
eliminates application downtime due to recompilation (timings depend on the 
number of invalid objects). The only database downtime required by the entire 
rolling upgrade process is the time it takes to perform a Data Guard switchover 
and the time for applications and services to be re-activated which can occur 
in a matter of a minute or two. 

A rolling upgrade can be performed using either SQL Apply or the Transient 
Logical Standby method. The two rolling upgrade methods are fairly similar 
where the primary difference is the state of the standby database before and 
after completing the upgrade. Using the SQL Apply method, the upgrade starts 
with one node as a logical standby and concludes with one node continuing to be 
a logical standby while with the transient logical standby, one node will start 
as a physical standby, temporarily convert to a logical standby, and will 
revert back to a physical standby after the upgrade. 

In the following guide, a rolling database migration using Data Guard SQL Apply 
will be deployed to migrate from Oracle Database 10g Release 2 (10.2.0.5) to 
Oracle Database 11g Release 2 (11.2.0.3). This same guide can also be used to 
perform rolling database upgrades using Data Guard SQL Apply. For example, 
upgrading Oracle Database 11g Release 2 (11.2.0.1) to (11.2.0.3).

http://www.idevelopment.info/data/Oracle/DBA_tips/Data_Guard/DG_60.shtml

Although the example in this guide demonstrates a rolling database migration,
the word upgrade will be used interchangeably with migration. 

----------------------------
Jeffrey M. Hunter, OCP
Sr. Database Administrator
jhunter@idevelopment.info
http://www.idevelopment.info
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