select /*+ parallel(t1, 1) */ count(* ) from t1;
select /*+ parallel(t1, 2) */ count(* ) from t1;
select /*+ parallel(t1, 3) */ count(* ) from t1;
select /*+ parallel(t1, 4) */ count(* ) from t1;
用到时, 再确认吧
原文：http://www.cnblogs.com/moveofgod/p/4225519.html