title: How to interpret ALL_TAB_COLS.DATA_LENGTH = 4000 for Oracle's CLOB types?
body: <p>When I create a table with a <code>CLOB</code> in it, the <code>CLOB</code> column is reported to have a <code>DATA_LENGTH</code> of 4000:</p>
  
  <pre><code>create table test (
    data clob
  );
  
  -- Returns 4000
  select data_length from all_tab_cols
  where table_name = 'TEST';
  </code></pre>
  
  <p>How can I interpret that? Is that some backwards-compatible tweak, considering that the limit for <code>VARCHAR2</code> is also 4000? Or is this to indicate that I can only insert / update string literals of length 4000? Is this behaviour of <a href="http://docs.oracle.com/cd/B28359_01/server.111/b28320/statviews_2090.htm" rel="nofollow"><code>SYS.ALL_TAB_COLS</code></a> documented somewhere?</p>