title: Row locking in case of DML
body: <p>I know that in case of DML statement row lock is acquired on the rows which are modified, but I am confused below of below statement from <a href="https://docs.oracle.com/cd/E11882_01/server.112/e41084/ap_locks001.htm#SQLRF55502" rel="nofollow noreferrer">this Oracle doc</a>:</p>
  <blockquote>
  <p><strong>A transaction that contains a DML statement does not require row locks
  on any rows selected by a subquery or an implicit query.</strong></p>
  <p>In the following sample UPDATE statement, the SELECT statement in
  parentheses is a subquery, &gt; whereas the WHERE a &gt; 5 clause is an
  implicit query:</p>
  <p><code>UPDATE t SET x = ( SELECT y FROM t2 WHERE t2.z = t.z ) WHERE a &gt; 5;</code></p>
  </blockquote>
  <p>My understanding is that lock will be acquired for all rows <code>WHERE a &gt; 5</code> but this article seems to be saying contrary.</p>
  <p>Could an Oracle expert please explain this.</p>