DB Mirroring / Auto-Failover, but ODBC?

Posted on 2010-08-18
Medium Priority
Last Modified: 2012-08-13
I think I have a problem.

I'm all excited about finally getting auto-failover in place for some of our databases, using High Safety configuration and mirroring.

For client apps, I know we can edit the connection strings to identify the failover server.

But...it just hit me that some of our backbone (third-party) applications use ODBC DSNs to identify our primary server.

Crap!  I really want to use this configuration, and not a Windows Server cluster or anything like that.

What are my options?  I cannot convert this app to use ODBC.  And I cannot convert it to allow OLEDB connections.

Thanks for any insight on this.
Question by:bamapie
LVL 42

Accepted Solution

dqmq earned 2000 total points
ID: 33470389
>What are my options?  I cannot convert this app to use ODBC.  And I cannot convert it to allow OLEDB connections.

That's a bit confusing because the issue was with respect to 3rd party app's that DO use ODBC.  In any case, if the ODBC DSN's are configured with the Native Client provider, then you do get the option for a Mirroring failover server.

Beyond that, you would need to look for some infrastructure in your network layer that redirects DNS assignments or reassigns IP addresses.  Not quite automatic, though.  


Expert Comment

ID: 33470391
I guess your infrastructure guys can add an entry to the DNS server that has the name of the failed server which maps to the new running server. Wouldn't something like re-directing solve your problem?


Expert Comment

ID: 33474030
High Availability operating mode provides durable synchronous transfer between the principal and mirror databases, as well as automatic failure detection and automatic failover.

High Safety operating mode transfers transactions synchronously, but it does not have a witness server. The synchronous transfer guarantees that all transactions committed at the principal are fi rst committed at the mirror, and it requires the same performance considerations as the High Availability operating mode. However, the lack of a witness prevents automatic failover to the mirror if the principal fails. If the principal fails in High Safety operating mode, you must promote the mirror manually to serve the database. Because High Safety operating mode’s synchronous transfer can affect application performance but does not offer the benefi t of automatic failover, this operating mode is not recommended for normal operations. You should confi gure a Database Mirroring session in High Safety operating mode only when you need to replace the existing witness server. After you have replaced or recovered the witness, you should change the operating mode back to High Availability operating mode.
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Expert Comment

ID: 33474047
in other words, you would not be able to use high safety mode for automatic failover.

Author Comment

ID: 33474804
dhlotter:  I mixed up my terms.  I meant High Availability.

Author Comment

ID: 33475385

>In any case, if the ODBC DSN's are configured with the Native Client provider,
>then you do get the option for a Mirroring failover server.

Where would I see / configure this?


Author Comment

ID: 33475689
Never mind, I see it.  Awesome.

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