Click here to monitor SSC
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 


DB mirroring and Log backup chain


DB mirroring and Log backup chain

Author
Message
JakeSA
JakeSA
Grasshopper
Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)

Group: General Forum Members
Points: 13 Visits: 37
In case of a Log Shipping, I'm aware that if you do if you do T-Log backup maybe through maintenance plan on the same machine (Primary), it will break the log backup chain on the secondary machine that receives the log.

However, in case of DB mirroring, if you do T-Log backup on the Mirroring Principal, does that break the log chain on the Mirroring Partner?
GilaMonster
GilaMonster
SSC-Forever
SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)

Group: General Forum Members
Points: 47187 Visits: 44356
There's no 'log chain' on a mirroring partner. Mirroring doesn't depend on log backups to copy transactions across (as log shipping does). You can't take log backups on a mirror DB (it's not online), only on the principal.


Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass


JakeSA
JakeSA
Grasshopper
Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)Grasshopper (13 reputation)

Group: General Forum Members
Points: 13 Visits: 37
GilaMonster (11/14/2011)
There's no 'log chain' on a mirroring partner. Mirroring doesn't depend on log backups to copy transactions across (as log shipping does). You can't take log backups on a mirror DB (it's not online), only on the principal.


Ok.

So it means that it will not mess up the mirrored database on the Mirroring partner if you do T-Log backup on the mirroring principal. Right?
GilaMonster
GilaMonster
SSC-Forever
SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)SSC-Forever (47K reputation)

Group: General Forum Members
Points: 47187 Visits: 44356
Yup.

But if you don't do log backups, it will mess up your principal. Log full errors aren't fun and the only thing that marks the log reusable in full recovery is a log backup.


Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass


Robert Davis
Robert Davis
SSCommitted
SSCommitted (1.7K reputation)SSCommitted (1.7K reputation)SSCommitted (1.7K reputation)SSCommitted (1.7K reputation)SSCommitted (1.7K reputation)SSCommitted (1.7K reputation)SSCommitted (1.7K reputation)SSCommitted (1.7K reputation)

Group: General Forum Members
Points: 1702 Visits: 1623
Just to clarify 1 point: there is a log chain on the mirror database. It has the exact same log chain as the principal. Without it, you wouldn't be able to fail over and bring the mirror online. Also, database mirroring will not allow you to do anything that will break the log chain. If you try to do something that would break the log chain, you will receive an error that you can't do that while the database is mirrored.

Another point: Taking a manual log backup of the log shipping primary does not break the log chain. what causes log shipping to fail is that the automated processes may not copy and restore that log backup causing a gap in the log sequence number on the secondary. You can remedy this by manually restoring (with NORECOVERY) the manual log backup on the secondary or by taking a differential backup that spans the missing gap and restoring it (with NORECOVERY) manually to secondary. After doing this, log shipping processes will be able to resume normal processing.

If you do need to take an out of band backup, it is recommended that you use the COPY_ONLY option as this generates the backup without updating the last LSN backed up.



My blog: SQL Soldier
Twitter: @SQLSoldier
My book: Pro SQL Server 2008 Mirroring
Microsoft Certified Master, SQL Server MVP
Database Engineer at BlueMountain Capital Management
Go


Permissions

You can't post new topics.
You can't post topic replies.
You can't post new polls.
You can't post replies to polls.
You can't edit your own topics.
You can't delete your own topics.
You can't edit other topics.
You can't delete other topics.
You can't edit your own posts.
You can't edit other posts.
You can't delete your own posts.
You can't delete other posts.
You can't post events.
You can't edit your own events.
You can't edit other events.
You can't delete your own events.
You can't delete other events.
You can't send private messages.
You can't send emails.
You can read topics.
You can't vote in polls.
You can't upload attachments.
You can download attachments.
You can't post HTML code.
You can't edit HTML code.
You can't post IFCode.
You can't post JavaScript.
You can post emoticons.
You can't post or upload images.

Select a forum

































































































































































SQLServerCentral


Search