title: Delete statement was very slow in Oracle
body: <p>I have a table with about 100k records and I want to delete some rows, The problem is that the <code>DELETE</code> statement is running very slowly - it didn't finish in 30 minutes. But the <code>select</code> statement was return in 1 second.</p>
  <p>The <code>SELECT</code> statement is as follows:</p>
  <pre><code>select * from daily_au_by_service_summary 
      where summary_ts &gt;= to_date('09-04-2012','dd-mm-yyyy') 
      order by summary_ts desc;
  </code></pre>
  <p>and <code>DELETE</code> statement is as follows:</p>
  <pre><code>delete from daily_au_by_service_summary 
      where summary_ts &gt; to_date('09-04-2012','dd-mm-yyyy');
  </code></pre>
  <p>This table have the only index at <code>summary_ts</code>.</p>
  <p>What could be the reason?</p>
  <p>EDIT: The problem had been resolved after I killed the sessions which locks the table, thanks all for the help.</p>
  <pre><code>SESSION_ID ORACLE_USERNAME                OS_USER_NAME                   OBJECT OWNER                   OBJECT_NAME                                                                                                                      OBJECT_TYPE         LOCKED_MODE
  ---------- ------------------------------ ------------------------------ ------------------------------ -------------------------------------------------------------------------------------------------------------------------------- ------------------- -----------
         213 T03RPT                         elou                           T03RPT                         DAILY_AU_BY_SERVICE_SUMMARY                                                                                                      TABLE                         3 
         203 T03RPT                         elou                           T03RPT                         DAILY_AU_BY_SERVICE_SUMMARY                                                                                                      TABLE                         3 
         202 T03RPT                         elou                           T03RPT                         DAILY_AU_BY_SERVICE_SUMMARY                                                                                                      TABLE                         3 
         190 T03RPT                         elou                           T03RPT                         DAILY_AU_BY_SERVICE_SUMMARY                                                                                                      TABLE                         3 
         189 T03RPT                         elou                           T03RPT                         DAILY_AU_BY_SERVICE_SUMMARY                                                                                                      TABLE                         3 
         188 T03RPT                         elou                           T03RPT                         DAILY_AU_BY_SERVICE_SUMMARY                                                                                                      TABLE                         3 
         187 T03RPT                         elou                           T03RPT                         DAILY_AU_BY_SERVICE_SUMMARY         
  </code></pre>