Switchover scenario in a cascaded standby setup

Question

Hi,
I have a setup of primary and standby databases in three locations A, B, C as below:
Database version: 11.1.7.0
In location A I have the primary database that ships redo log to a physical standby at location B alone.
In location B I have a physical standby that replicates to site C.
In site C I have the final physical standby that receives its redo logs directly from site B. In essence, this is a cascaded standby database.
My question is about the switchover:
Currently, both the instances in sites A and B have the LOG_ARCHIVE_DEST_3 set to point to site C and this is valid for standby role alone.
Which means in case the two sites - A & B reverse roles, site C will continue receiving redo logs from either A or B, depending on which one is the new standby.
However, the doubt comes in if site C were to become the new primary instance. I suspect that I would need to add two parameters LOG_ARCHIVE_DEST_2 and LOG_ARCHIVE_DEST_3 and point them to sites A and B respectively, and make them valid only for the primary role. In this case, if site C becomes the new primary, then both sites A and B can continue receiving redo logs from site C.
Anyone who has ever implemented this?
Regards,
dula

Answer 1

The scenario in the doc. may also help you:
http://download.oracle.com/docs/cd/B28359_01/server.111/b28294/cascade_appx.htm#i638620
Example E-1 Sample Use of Initialization Parameters in Cascaded Destinations
Boston Database (Primary Role)
DB_UNIQUE_NAME=boston
REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE
LOG_ARCHIVE_CONFIG='DG_CONFIG=(chicago,boston,denver)'
LOG_ARCHIVE_DEST_1='LOCATION=/arch1/boston/ VALID_FOR=(ALL_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=boston'
LOG_ARCHIVE_DEST_2= 'SERVICE=denver VALID_FOR=(STANDBY_LOGFILES,STANDBY_ROLE) DB_UNIQUE_NAME=denver'
LOG_ARCHIVE_DEST_3= 'SERVICE=chicago VALID_FOR= (ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=chicago'
Chicago Database (Standby Role)
DB_UNIQUE_NAME=chicago
LOG_ARCHIVE_CONFIG= 'DG_CONFIG=(chicago,boston,denver)'
REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE
LOG_ARCHIVE_DEST_1= 'LOCATION=/arch1/chicago/ VALID_FOR=(ALL_LOGFILES,ALL_ROLES) DB_UNIQUE_NAME=chicago'
LOG_ARCHIVE_DEST_2= 'SERVICE=denver VALID_FOR=(STANDBY_LOGFILES,STANDBY_ROLE) DB_UNIQUE_NAME=denver'
LOG_ARCHIVE_DEST_3= 'SERVICE=boston VALID_FOR= (ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=boston'
Denver Database (Standby Role)
DB_UNIQUE_NAME=denver
LOG_ARCHIVE_CONFIG= 'DG_CONFIG=(chicago,boston,denver)'
REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE
LOG_ARCHIVE_DEST_1= 'LOCATION=/arch1/denver/ VALID_FOR=(ONLINE_LOGFILES,ALL_ROLES) DB_UNIQUE_NAME=denver'
LOG_ARCHIVE_DEST_2= 'LOCATION=/arch2/denver/ VALID_FOR=(STANDBY_LOGFILES,STANDBY_ROLE) DB_UNIQUE_NAME=denver'
Both the Boston primary database and the Chicago physical standby database define the LOG_ARCHIVE_DEST_2 initialization parameter as SERVICE=denver VALID_FOR=(STANDBY_LOGFILES, STANDBY_ROLE). Hence, even if the Boston and Chicago databases switch roles, the redo data will continue to be forwarded to the Denver database. Remember, as part of the original setup of the physical standby database, you should define a local destination, VALID_FOR=(ALL_LOGFILES, PRIMARY_ROLE), that will be used for local archiving when the physical standby database transitions to the primary role.