Presuming the definition of "loss" includes "data is unrecoverable on the Principal after the outage"....

The answer is the most hated expression "it depends". Given the conditions where the Force Service command can be used (Principal down, Witness OFF or connected to Mirror), the potential definitely exists for data loss. See the following link for more detail. http://msdn.microsoft.com/en-us/library/ms189270.aspx

The "potential" component relates to queued transaction log blocks that were being transmitted but not yet committed to disk on the Mirror when the Principal went down. If your system is particularly active the potential for loss is high...based on a collision of the failure and the transmit/commit cycle. If your system is not so active and the Mirror failure occurred when the Mirror was synchronized there would be no loss.

HTH

mreed

Pragmatic Works