Oracle Database - Enterprise Edition - Version 184.108.40.206 to 220.127.116.11.0 [Release 9.2 to 11.2]
Information in this document applies to any platform.
***Checked for relevance on 25-JUNE-2013***
Before we initiate the switchover, we check the synchronization status between primary and physical standby. They are in perfect sync. Physical standby has applied the lastly generated archived redo log sequence. But in physical standby v$database.switchover_status shows "not allowed"
It is expected to see this status in physical standby.
When we are certain that Primary and target standby are in sync,
We can then proceed with switchover exercise regardless of "not allowed" status in Physical standby
Switchover always originates from Primary database.
On the request of switchover sql statement
"alter database commit to switchover to physical standby with session shutdown",
Primary will generate special marker called EOR (end-of-redo) that is placed in the
header of online redo log sequence. So this online redo log sequence will be archived locally
and sent to all standby databases.
Only upon receiving and applying EOR (end-of-redo), v$database.switchover_status will change
from "not allowed" to "to primary" or "sessions active".
At this stage Physical standby is ready to assume Primary database role
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