Today we are going to see how can we attach data file exists in network share with the help of trace flag 1807. By default SQL Server 7,2000 and 2005 will not allow you to attach data file that exists in network share. This is the default behavior because attach database file from network share is overhead as performance is the great factor because if network share is slow or if disruptions happen in the network share will make the database to go offline. However in some circumstances we require this to be done for testing purpose. You will be getting anyone of the error below if you try to attach the data file from network share (without using trace flag 1807).