title: How to fix undo retention size on oracle db
body: <p>I want to update  millions of records on the table.When İ execute my query it gives error after 10 minutes</p>
  <p>Error like this : <code>snapshot too old: rollback segment number 1853 with name .... too small</code></p>
  <p>I tried <code>ALTER SYSTEM SET UNDO_RETENTION</code> = 86400; but error is continues..</p>
  <p>I tried <code>ALTER SYSTEM SET UNDO_MANAGEMENT = AUTO </code> but  oracle gives that  error <code>The specified initialization parameter is not modifiable</code>
  `</p>