Remove the Witness from a Database Mirroring Session

At any time during a database mirroring session, the database owner can turn off the witness for a database mirroring session.

Turning off the witness changes the operating mode in accordance with the transaction-safety setting:

• If transaction safety is set to FULL (the default), the session uses high-safety, synchronous mode without automatic failover. For more information, see Synchronous Database Mirroring (High-Safety Mode).
  
  
• If transaction safety is set to OFF, the session operates asynchronously (in high-performance mode) without requiring quorum. Whenever transaction safety is turned off, we strongly recommend also turning the witness off. For more information, see Asynchronous Database Mirroring (High-Performance Mode).

The transaction safety setting of the database is recorded on each partner in the sys.database_mirroring catalog view in the mirroring_safety_level and mirroring_safety_level_desc columns. For more information, 

To turn off the witness

1. Connect to either partner.
   
   
2. Issue the following statement:
   
   ALTER DATABASE <database_name> SET WITNESS OFF
   where <database_name> is the name of the mirrored database.
   
   Ref: MSDN