title: Change the datatype of a column in a partitioned table with billion rows
body: <p>We have a table with 120 partitions on date range which in turn is subpartitioned again on range.</p>
  
  <p>Each partition has around 200 million records, the conventional way of changing the datatype will make our production unresponsive for hours.Is there any better way for changing the datatype of such a huge table?</p>
  
  <p>We have already tried the following options:</p>
  
  <ol>
  <li>Exchange partition. This does not work.</li>
  <li>Create a new table with the same structure as the existing one and the altered column, and inserting the data using /*+ append *. It again takes hours.</li>
  </ol>
  
  <p>Currently the column size is varchar2(30). We need to change it to: </p>
  
  <pre><code>ALTER TABLE ORDERS MODIFY (INFO VARCHAR2(50) );
  </code></pre>