mipo, Could you do the deletes in several, smaller batches?
WHERE DateDiff(mm,transactiondatestamp,GetDate()) = 4
.
.
WHERE DateDiff(mm,transactiondatestamp,GetDate()) = 3
Or, if it's particularly large, maybe do DateDiff(dd,transactiondatestamp,GetDate()) = 90, then 89.
Regards,
SJTerrill