Active Session History (ASH) Performed An Emergency Flush Messages In The Alert Log

傷城~ 2022-08-11 17:29 72阅读 0赞

<table> 
 <tbody> 
  <tr> 
   <td align="left"><span style="font-size:14px; text-align:right; padding:0px 6px 0px 0px; font-weight:bold">Active Session History (ASH) Performed An Emergency Flush Messages In The Alert Log (文档 ID 1385872.1)</span></td> 
   <td align="right">&nbsp;</td> 
   <td><img src="/images/20220810/afbb0265e0d64f5589fb214ac54e1bd0.png" alt="" width="20" height="10"></td> 
  </tr> 
 </tbody> 
</table>

--------------------

![t.gif][]

<table style="table-layout:fixed; overflow:hidden"> 
 <tbody> 
  <tr> 
   <td style="overflow:hidden"><span style="font-size:12px"></span> <p><strong>In this Document</strong><br> </p> 
    <table> 
     <tbody> 
      <tr> 
       <td></td> 
       <td><a href="https://support.oracle.com/epmos/faces/SearchDocDisplay?_adf.ctrl-state=vn64sw15v_4&amp;_afrLoop=1995895300148098#SYMPTOM" rel="nofollow">Symptoms</a></td> 
      </tr> 
     </tbody> 
    </table> 
    <table> 
     <tbody> 
      <tr> 
       <td>&nbsp;</td> 
       <td><a href="https://support.oracle.com/epmos/faces/SearchDocDisplay?_adf.ctrl-state=vn64sw15v_4&amp;_afrLoop=1995895300148098#CAUSE" rel="nofollow">Cause</a></td> 
      </tr> 
     </tbody> 
    </table> 
    <table> 
     <tbody> 
      <tr> 
       <td>&nbsp;</td> 
       <td><a href="https://support.oracle.com/epmos/faces/SearchDocDisplay?_adf.ctrl-state=vn64sw15v_4&amp;_afrLoop=1995895300148098#FIX" rel="nofollow">Solution</a></td> 
      </tr> 
     </tbody> 
    </table> 
    <hr> <p><br> </p> 
    <table> 
     <tbody> 
      <tr> 
       <td><em>This document is being delivered to you via Oracle Support's Rapid Visibility (RaV) process and therefore has not been subject to an independent technical review.<em></em></em></td> 
      </tr> 
     </tbody> 
    </table> <h2 style="border-bottom-width:1px; border-bottom-style:solid; border-bottom-color:rgb(196,209,230); font-size:16px; background-color:rgb(119,119,115); color:rgb(255,255,255); text-transform:uppercase; padding-top:6px; padding-bottom:6px; padding-left:8px"> APPLIES TO:</h2> Oracle Database - Enterprise Edition - Version 11.1.0.6 and later<br> Information in this document applies to any platform.<br> <h2 style="border-bottom-width:1px; border-bottom-style:solid; border-bottom-color:rgb(196,209,230); font-size:16px; background-color:rgb(119,119,115); color:rgb(255,255,255); text-transform:uppercase; padding-top:6px; padding-bottom:6px; padding-left:8px"> <a rel="nofollow"></a>SYMPTOMS</h2> <p>Periodically see the following message in the alert log.<br> <br> Active Session History (ASH) performed an emergency flush. This may mean that ASH is undersized. If emergency flushes are a recurring issue, you may consider increasing ASH size by setting the value of _ASH_SIZE to a sufficiently large value. Currently, ASH size is &lt;some value&gt; bytes. Both ASH size and the total number of emergency flushes since instance startup can be monitored by running the following query: select total_size,awr_flush_emergency_count from v$ash_info;</p> <h2 style="border-bottom-width:1px; border-bottom-style:solid; border-bottom-color:rgb(196,209,230); font-size:16px; background-color:rgb(119,119,115); color:rgb(255,255,255); text-transform:uppercase; padding-top:6px; padding-bottom:6px; padding-left:8px"> <a rel="nofollow"></a>CAUSE</h2> <p>Typically some activity on system causes more active sessions, therefore filling the ASH buffers faster than usual causing this message to be displayed. It is not a problem per se, just indicates the buffers might need to be increased to support peak activity on the database.</p> <h2 style="border-bottom-width:1px; border-bottom-style:solid; border-bottom-color:rgb(196,209,230); font-size:16px; background-color:rgb(119,119,115); color:rgb(255,255,255); text-transform:uppercase; padding-top:6px; padding-bottom:6px; padding-left:8px"> <a rel="nofollow"></a>SOLUTION</h2> <p>The current ASH size is displayed in the message in the alert log, or can be found using the following SQL statement.</p> 
    <div style="overflow:auto; border:1px solid rgb(196,209,230); padding:0.5em; margin:5px 0px 0px; font-family:'Courier New',Courier,monospace; font-size:12px; background-color:rgb(224,234,241)">
      select total_size from v$ash_info; 
    </div> <p>Then increase the value for _ash_size by some value, like 50% more than what is currently allocated.&nbsp; For example if total_size = 16MB, then an increase of 50% more would be (16MB + (16MB * 50%)) = 24MB.&nbsp;</p> 
    <div style="overflow:auto; border:1px solid rgb(196,209,230); padding:0.5em; margin:5px 0px 0px; font-family:'Courier New',Courier,monospace; font-size:12px; background-color:rgb(224,234,241)">
      sqlplus / as sysdba 
     <br> alter system set "_ash_size"=25165824; 
    </div> <p>You can verify the change using the following select:</p> 
    <div style="overflow:auto; border:1px solid rgb(196,209,230); padding:0.5em; margin:5px 0px 0px; font-family:'Courier New',Courier,monospace; font-size:12px; background-color:rgb(224,234,241)">
      select total_size from v$ash_info; 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

[t.gif]: /images/20220810/afbb0265e0d64f5589fb214ac54e1bd0.png