May 18, 2012 at 1:08 am
Hi All,
I have been through Many interviews and this Question has been asked to me various Time but as I am New to Mirroring I need to understand What Happens if the Mirrored Server is Down .
Does it Impact the Production Server
Details :
Servers are of same configuration
HIGH bandwidth Allocated through Network
HIGH Protection with Manual Failover
I would Appreciate if some body can help me with Both the Scenarios ..Like Manual And AUTOMATIC failover ....
PLEASE MAKE SURE I AM AASKING IF MIRRORED/SECONDARY SERVER GOES DOWN.WHAT WOULD BE THE PROCESS/IMPACT happening on the Primary Server in high Protection Plan.
May 18, 2012 at 1:53 am
http://msdn.microsoft.com/en-us/library/dd207006.aspx and http://msdn.microsoft.com/en-us/library/ms189902.aspx
When the witness becomes unavailable the Principal can still be used but the mirroring state is DISCONNECTED. The log file of the principal will continue to expand until mirroring is working again or other action is taken to remove mirroring.
An excellent book for this is Wrox 'Professional Microsoft SQL Server 2008 Administration" - Chapter 17.
May 18, 2012 at 11:34 am
You didn't indicate there was a witness, so this answer applies to a non-witnessed set-up. If the mirroring session is in High Protection mode and the mirror database becomes unavailable, the Principal database will continue to be available. It will display "Principal, Disconnected" in Management Studio meaning that transactions in the database are not being communicated to the (unavailable) mirror partner. However the Principal database will accept transactions in this state.
Once the secondary (mirror) database becomes available again, the transactions from the log of the Principal will be written to it so that the two databases become synchronized once more.
elliott
May 18, 2012 at 11:38 am
Elliott Berkihiser (5/18/2012)
You didn't indicate there was a witness, so this answer applies to a non-witnessed set-up. If the mirroring session is in High Protection mode and the mirror database becomes unavailable, the Principal database will continue to be available. It will display "Principal, Disconnected" in Management Studio meaning that transactions in the database are not being communicated to the (unavailable) mirror partner. However the Principal database will accept transactions in this state.Once the secondary (mirror) database becomes available again, the transactions from the log of the Principal will be written to it so that the two databases become synchronized once more.
elliott
It also means that your transaction log will not be truncated (VLF marked as unused) by transaction log backups on the principal server until the mirrored server is back up and synced with the principal.
This could have an impact if your transaction log should happen to fill your disk drive or it reaches its maximum size.
May 18, 2012 at 12:55 pm
Agreed. That's an important point. If the mirror is going to be down for long, it might be best to remove the mirroring (Alter Database MyDatabase Set Partner OFF), and re-establish mirroring when the problem is fixed.
//elliott
May 24, 2012 at 3:58 am
Thanks All for your Clear and Wonderful Answers
Viewing 6 posts - 1 through 5 (of 5 total)
You must be logged in to reply to this topic. Login to reply