looks like he is trying to get the user with the most recent activity to the top of the resultset.

I cannot find anything regarding selective truncation of the transaction log. Apparently its an all or nothing prospect that should happen automatically.

http://technet.microsoft.com/en-us/library/ms189085.aspx explains the truncation process.

Additionally...

Not knowing what your data looks like, you are testing for an exact match on timestamp, but not testing for the existence of rows at that timestamp beforehand. ...

I see where you are going with sp2, but what are you doing in sp1? Would it be possible to create sp1 as a view instead? ...