spid -4 blocking the transactions

Hi All,

We encountered a situation today where the spid -4 was blocking the transactions. We're not able to kill it as it was not treated as a valid spid by SQL server. We tried to get the UOW using below query but no result was returned.

select * from master..syslockinfo
where req_spid = -4

Since this was not a production impacting server we restarted the SQL Service as we didnt have any other option.
We've learned that it might be the orphan transctions of MSDTC.

However, I need to understand what can be done to resolve this issue as I cannot restart SQL Server for this.

Please help!

Regards
Mayur Kashikar