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Roo avatar image
Roo asked

Database Mirroring Transaction Log Back Up

Hello.

I am planning to set up database mirroring of my Live principal database in the next few days. However, after reading a few confusing articles on the web, I am not too sure about the transaction Log status of the Mirrored database.

So, please can somebody tell me that if I back up the transaction log file of the principal database (which will truncate the queries that have already been run, and sent to the mirror), will this also backup the log file on the Mirror database and truncate the queries that have already been applied to the mirror?

I am effectively trying to prevent the mirror transaction log file from growing too large and need to have a way of controlling its size.

Plus, is there a way estimating the size of the mirrored log whilst it is in the 'no recovery' state?

Thanks for all the help in advance it is much appreciated!!!!

sql-server-2005mirroring
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Jason Cumberland avatar image
Jason Cumberland answered

You can safely back up the log on the primary (and you have to or it will fill up) and it will not affect the mirror. The transactions are committed on the mirror as they are passed over the wire and not written to the transaction log. The mirror's transaction log size should remain constant until the database is recovered.

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