Negative Number in SPID

Solution 1:

According to the documentation for blocking_session_id

-5 = Session ID of the blocking latch owner could not be determined because it is not tracked for this latch type (for example, for an SH latch).

Edit: I came across this from a Microsoft engineer. The bit I found interesting:

A​​ blocking session id of -5 alone does not indicate a performance problem. ​​ The addition of -5 is just an indication that the session is waiting on an asynchronous action to complete where-as​​ prior to the addition,​​ the same session wait would have showed​​ blocking session = 0​​ but​​ was still in a wait state.