800 users use table 'Purchase' for select, insert, update. At the same time I want to update the purhcase table which affects 200,000 rows. (update d set d.venor = abcd from purchase d (nolock) where d.id <= 500000). This update statment blocks the users, they say they could not use the application or application is slow etc when update runs.
How to update this 200,000 rows or more without giving any blocking to the users. Pls help.