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1) Is it possible to build stand by databases with same instance name of legacy primary instances? If so, how it could be?
Yes. Not sure I understand the second part of the question. I like to think of a standby database and a primary database as the same database in different modes. RMAN treats them as the same. They have the same DBID.
2) If not, we can build stand by database with different instance name (DB_UNIQUE_NAME). Do the switch over and cut off the replication with legacy primary database. Once done, What other alternative do we have to change the instance name same like legacy database instances?
It should not matter what the database name is. Almost everything connects using an Alias. I find it easier to use a slightly different name for the Standby because then I know which site I'm working on. What I did was put an S in front of the name on the standby side to keep them apart in my mind. A tnsnames entry can handle the rest. So yes you can do that, but it might be harder to keep track that way.
ernie = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = primary.server)(PORT = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = standby.server)(PORT = 1521)) ) (CONNECT_DATA = (SERVICE_NAME = ernie) ) )
Thanks for your quick response. I forgot to explain my complete requirement.
The plan is to move all the databases from legacy to new servers using Data Guard to minimize the downtime. The name, SID of DG site would be the same like legacy system .Once it will be validated by consumers, we will cut off replication to legacy and later drop the legacy database.
The reason behind that there are unknown application which connects to database using instance name not DB name and if we don't retain the same name, those will see impact after migration which we don't want.
Please assist the best way to accomplish this requirement.
OK then just use the name you want. You can use same name.
DB_NAME should be same.
DB_UNIQUE_NAME should be different.
It works either way, nothing special. So I use different so my SID on the primary is PRIMARY and its STANDBY on the standby. You would just use the same SID ( as before ) its as simple as that.
DB_UNIQUE_NAME attribute is introduced to clearly identify the relationship between a primary and standby databases.
Also of interest
Oracle data guard configuration for primary and standby db_name
Edited by: mseberg on Feb 22, 2013 3:13 PM