title: Oracle error ORA-25188 spontaneously appearing for unknown reasons
body: <p>A remote installation of some software using Oracle 11.2 is being reported with the following errors:</p>
  
  <ul>
  <li>ORA-25188: cannot drop/disable/defer the primary key constraint for
  index-organized tables or sorted hash cluster</li>
  </ul>
  
  <p>These errors seem to be happening everywhere.  Even for basic inserts.  As far as I can tell, I don't drop or alter any indexes in my IOT tables. And I've never had any issues like this in the past few years (the software hasn't changed much). The other thing I should mention is that these errors just started popping up after several days of error-free activity.</p>
  
  <p>So I got a dump of the entire schema.  I then imported it into my own Oracle system, and connected my application to it.  Everything works fine!  I don't have easy access to the actual system, so I am not able to investigate directly.</p>
  
  <p>Is there any indirect reason why the system could be generating ORA-25188 or some bad state that could cause this error? </p>