Principal Mirroring server databases go in recovery when mirror server is turned off

When I turn on the mirror database server the primary database server databases will go in recovery. The only way i have found to resolve this is to turn back on the mirror server. There is a witness server as well in the setup. The servers are Windows 2008 R2 with SQL Server 2008 R2.
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lcohanDatabase AnalystCommented:
Why would you turn OFF the mirror server?

Database mirroring maintains two copies of a single database that must reside on different server instances of SQL Server Database Engine. Typically, these server instances reside on computers in different locations. One server instance serves the database to clients (the principal server). The other instance acts as a hot or warm standby server (the mirror server), depending on the configuration and state of the mirroring session. When a database mirroring session is synchronized, database mirroring provides a hot standby server that supports rapid failover without a loss of data from committed transactions. When the session is not synchronized, the mirror server is typically available as a warm standby server (with possible data loss).

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beck4164Author Commented:
We reboot the mirror server to the most recent shutdown was caused as we were moving the data center the server lived in.

When I shutdown the mirror server most recently I would expect the principal server to continue to function normally and the databases remain online. I wouldn't expect to see them go in recovery when I shutdown the mirror server.

Any ideas what it happens that way?
lcohanDatabase AnalystCommented:
It is all in the above between the quotes - you can't shotdown the mirror because sync or async they need to and talk to each other. If you would just take a full backup from one box and restore it to another box then yes, you could shutdown the server where you restored it but as long as you setup mirroring they both have to be up.

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