BACKUP LOG "pathtomylogfile" WITH TRUNCATE_ONLY;
And I get this error:
Msg 155, Level 15, State 1, Line 1
'TRUNCATE_ONLY' is not a recognized BACKUP option.
So I asked myself if there is an option similar to what 'TRUNCATE_ONLY' was doing in 2005?
I posted a query at Ask Sql Server Central
I got very nice responses, including a link to this article by Brent Ozar
Check out the responses above, hope it helps you if you are upgrading to Sql Server 2008.
You can also read further on this article on how to configure Sql Server 2008