如果a没有索引，以下SQL会对表加S锁：db2 +c "select * from t1 where a=4 with rr"db2 +c "delete from t1 where a=3" , 需要表的IX锁,  IX锁和S锁是不兼容的，不可能执行成功。

You might want to read http://www-01.ibm.com/support/kn ... c/doc/c0004962.html"Big-block reads    A read where several pages (usually an extent) are retrieved in a single request. Reading several pages at once is more efficient than readin...