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If you want to upgrade or install a patch on two separate instances that house both the principal and mirrored database, how can you go about that? If the database that is being mirrored needs to be available 24/7 and you don't have a window to go offline, what is the best means to do this?

EDIT: this is with SQL Server.

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up vote 1 down vote accepted

Assuming SQL Server, you'll want to apply the patch to the mirror, then failover and apply the patch to the server that was active (and is now the mirror). This way you only have to take one outage as you only need to fail over once.

If you are doing an actual version upgrade SQL 2008 to SQL 2008 R2 for example this is a little different.

No matter what there will be an outage that you have to take.

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