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Home » SQL Server 2008 » SQL Server 2008 High Availability » Tlog backup on princple server?
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ananda.murugesan
Posted Wednesday, December 14, 2011 5:07 AM
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Hi,

one of the production server TLog backup taken every 30 minutes. the same server going to implement HA for database mirroring.

Mirroring transfer TLog to mirror server from principal server, In this case
what frequency TLog backup to be set in principal server after implemented mirroring.

Pl.let me know once completed database mirroring between principal and mirror server, Is it really required or possibility to take TLOG backup at principal server?

thanks
ananda
Post #1221547
Dev
Posted Wednesday, December 14, 2011 5:17 AM


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You can take Log Backups on Primary Server.

~Dev~
Post #1221553
Dev
Posted Wednesday, December 14, 2011 5:20 AM


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Sorry missed the second part of question.

You should keep taking log backup at regular interval for Transaction Logs truncation. 30 minutes interval is fine.

~Dev~
Post #1221557
ananda.murugesan
Posted Wednesday, December 14, 2011 5:22 AM
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Dev (12/14/2011)
You can take Log Backups on Primary Server.


ok, If i have taken log backup every 30 min at principal server then what is frequency for Tlog apply at mirror server?

thanks
ananda
Post #1221560
Dev
Posted Wednesday, December 14, 2011 5:29 AM


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ananda.murugesan (12/14/2011)
Dev (12/14/2011)
You can take Log Backups on Primary Server.


ok, If i have taken log backup every 30 min at principal server then what is frequency for Tlog apply at mirror server?

thanks
ananda


What is the operation mode High Safety / High Performance?

~Dev~
Post #1221564
Dev
Posted Wednesday, December 14, 2011 5:31 AM


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FYI...

A database mirroring session runs with either synchronous or asynchronous operation. Under asynchronous operation, the transactions commit without waiting for the mirror server to write the log to disk, which maximizes performance. Under synchronous operation, a transaction is committed on both partners, but at the cost of increased transaction latency.

There are two mirroring operating modes. One of them, high-safety mode supports synchronous operation. Under high-safety mode, when a session starts, the mirror server synchronizes the mirror database together with the principal database as quickly as possible. As soon as the databases are synchronized, a transaction is committed on both partners, at the cost of increased transaction latency.

The second operating mode, high-performance mode, runs asynchronously. The mirror server tries to keep up with the log records sent by the principal server. The mirror database might lag somewhat behind the principal database. However, typically, the gap between the databases is small. However, the gap can become significant if the principal server is under a heavy work load or the system of the mirror server is overloaded.

In high-performance mode, as soon as the principal server sends a log record to the mirror server, the principal server sends a confirmation to the client. It does not wait for an acknowledgement from the mirror server. This means that transactions commit without waiting for the mirror server to write the log to disk. Such asynchronous operation enables the principal server to run with minimum transaction latency, at the potential risk of some data loss.

~Dev~
Post #1221567
baabhu
Posted Sunday, December 18, 2011 10:34 PM


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In mirroring Transaction log backup will not be applied on the secondary server. However the uncommitted/commited transaction will be automatically applied to the secondary database server log. To manage the size of the transaction log in the primary server, we need to have transaction log backup at scheduled interval.

Read the article from techet.

http://technet.microsoft.com/en-us/library/cc917680.aspx


-- Babu
Post #1223620
GilaMonster
Posted Monday, December 19, 2011 3:09 AM


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ananda.murugesan (12/14/2011)
Dev (12/14/2011)
You can take Log Backups on Primary Server.


ok, If i have taken log backup every 30 min at principal server then what is frequency for Tlog apply at mirror server?


You're thinking of log shipping.

In database mirroring the log records are copied across by the mirroring functionality either before the transaction commits (synchronous) or shortly after (asynchronous). You have to take log backups to keep the log from growing and to ensure you can restore to an earlier point if necessary. The log backups aren't copied across and applied, that's log shipping.

Gail Shaw
Microsoft Certified Master: SQL Server 2008, MVP
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

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Post #1223701
GilaMonster
Posted Monday, December 19, 2011 3:11 AM


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Dev (12/14/2011)
FYI...

A database mirroring session runs with either synchronous or asynchronous operation....


If you're going to quote someone else's work (in this case Books Online), the correct thing to do is to reference it properly. Otherwise you're implying that it's your own work.
In this case. http://msdn.microsoft.com/en-us/library/ms189852.aspx

Gail Shaw
Microsoft Certified Master: SQL Server 2008, MVP
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

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Post #1223703
Dev
Posted Monday, December 19, 2011 3:45 AM


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GilaMonster (12/19/2011)
Dev (12/14/2011)
FYI...

A database mirroring session runs with either synchronous or asynchronous operation....


If you're going to quote someone else's work (in this case Books Online), the correct thing to do is to reference it properly. Otherwise you're implying that it's your own work.
In this case. http://msdn.microsoft.com/en-us/library/ms189852.aspx


It was not my intension (never thought it). I didn’t want OP to be lost in BOL so I identified what he needed and pasted it here.

p.s. hope I didn’t violet any copyright

~Dev~
Post #1223714
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