title: Can someone explain ORA-29861 error in plain english and its possible cause?
body: <p>I have an application implemented in Grails framework using underlying Hibernate. After it runs for a while, I got an Oracle DB error and resolved it by rebuilding the offending index. I wonder if anyone can propose the possible cause(s) and ways to prevent it from happening.</p>
  
  <blockquote>
    <p>Caused by:
    org.springframework.jdbc.UncategorizedSQLException:</p>
    
    <p>Hibernate operation: Could not execute JDBC batch update; 
    uncategorized SQLException for SQL [update RSS_ITEM set guid=?, 
    pubdate=?, link=?, rss_source_id=?, title=?, description=?, 
    rating_raw=?, rating_tuned=?, date_created=?, date_locked=? where 
    RSS_ITEM_ID=?]; SQL state [99999]; error code [29861]; ORA-29861: 
    domain index is marked LOADING/FAILED/UNUSABLE </p>
    
    <p>; nested exception is java.sql.BatchUpdateException:
    ORA-29861: 
    domain index is marked LOADING/FAILED/UNUSABLE</p>
  </blockquote>