UPDATE QUERY can't update table

Hi,

During 1500-2000 concurrent users, DB Transaction locks occur. So that Update query can't update table and we get inconsistent data. How can we avoid this inconsistent data?? Why we get transaction locks??

Eg. In update query it update the status of user with completed; but because of transaction lock  update query can't update status of user it remains uncompleted. So we can get wrong status of user(inconsistent data). Why UPDATE query update the status of user???

update table set status='completed', date=@p2,score=@p3 where id=@p1