title: How to define Oracle BLOB length
body: <p>I encount a <code>BLOB</code> column in my project,and the <code>DATA_LENGTH</code> column was 4000!</p>
  
  <p>And how to define a <code>BLOB</code> length? </p>
  
  <p>Can Oracle <code>BLOB</code> could define length?</p>
  
  <p>I find to Oracle reference and Internet and get nothing.</p>