Incase you want to change the mode of the mirroring from High Performance to High Safety. You can do it from the command line.

ALTER DATABASE SET PARTNER SAFETY OFF;

Please note that SQL Server 2008 Standard Edition does not allow changing the safety level. It will throw the below error

“Msg 1473, Level 16, State 6, Line 2
This SQL Server edition does not allow changing the safety level. ALTER DATABASE command failed”