SQL Server may report a blocking session id as a negative integer value. SQL Server uses negative sessions ids to indicate special conditions.
Value
Description
-1
Orphaned lock, commonly a bug in SQL Server where lock ownership has been incorrectly lost.
-2
Pending DTC transaction. The client connection(s) associated with the DTC transaction have disconnected and the SQL Server DTC transaction object is waiting for the MSDTC Manager, state change notification. The client application needs to invoke commit or rollback on the transaction interface to complete the DTC transaction.
-3
Deferred recovery. The