appf_ocm.htm

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<h3>
<font face="arial, helvetica, sans-serif" color="#330099">
Starting the Cluster Manager<a id="sthref780" name="sthref780"></a>
</font>
</h3>
<p>To start the Cluster Manager:
</p>
<ol type="1" start="1">
<li>
<p>Confirm that the Watchdog daemon is running.
</p>
</li>
<li>
<p>Confirm that the host names specified by the PublicNodeNames and PrivateNodeNames parameters in the<code> cmcfg.ora</code> file are listed in the <code>&#047;etc&#047;hosts</code> file.
</p>
</li>
<li>
<p>As the <code>root</code> user, start the <code><a id="sthref781" name="sthref781"></a>oracm</code> process as a background process. Redirect any output to a log file. For example, enter the following:
</p>
<pre>&#036; su root
&#035; cd &#036;ORACLE&#095;HOME&#047;oracm&#047;bin
&#035; oracm &lt;&#047;dev&#047;null &gt;&#036;ORACLE&#095;HOME&#047;oracm&#047;log&#047;cm.out 2&gt;&amp;1 &amp;

</pre>
<p>In the preceding example, all of the output messages and error messages are written to the <code>&#036;ORACLE&#095;HOME&#047;oracm&#047;log&#047;cm.out</code> file.
</p>
</li>
</ol>
<p>The <code>oracm</code> process spawns multiple threads. To list all of the threads, enter the <code>ps&#160;-elf</code> command.
</p>
<p><a href="#CACJHGEH">Table F-3</a> describes the arguments of the <code>oracm</code> executable.
</p><a id="sthref782" name="sthref782"></a><a id="CACJHGEH" name="CACJHGEH"></a>
<p><strong><em><font face="arial, helvetica, sans-serif">Table F-3 Arguments for the oracm Executable
</font></em></strong></p>
<table title="Arguments for the oracm Executable" summary="This table describes the arguments of the oracm executable." dir="ltr" border="1" width="100%" frame="hsides" rules="groups" cellpadding="3" cellspacing="0">
<thead>
<tr align="left" valign="top">
<th id="r1c1" align="left" colspan="1" rowspan="1" valign="bottom">
<font face="Arial, Helvetica, sans-serif">
<strong>Argument
</strong></font></th>
<th id="r1c2" align="left" colspan="1" rowspan="1" valign="bottom">
<font face="Arial, Helvetica, sans-serif">
<strong>Values
</strong></font></th>
<th id="r1c3" align="left" colspan="1" rowspan="1" valign="bottom">
<font face="Arial, Helvetica, sans-serif">
<strong>Default Value
</strong></font></th>
<th id="r1c4" align="left" colspan="1" rowspan="1" valign="bottom">
<font face="Arial, Helvetica, sans-serif">
<strong>Description
</strong></font></th>
</tr>
</thead><tbody>
<tr align="left" valign="top">
<td id="r2c1" headers="r1c1" align="left" colspan="1" rowspan="1">&#047;a:<em><code>action</code></em>
</td>
<td headers="r2c1 r1c2" align="left" colspan="1" rowspan="1">0,1
</td>
<td headers="r2c1 r1c3" align="left" colspan="1" rowspan="1">0
</td>
<td headers="r2c1 r1c4" align="left" colspan="1" rowspan="1">Specifies the action taken when the LMON process or another Oracle process that can write to the shared disk terminates abnormally.
<p>If <code>action</code> is set to 0 (the default), no action is taken. If <code>action</code> is set to 1, the Cluster Manager requests the Watchdog daemon to stop the node completely.
</p>
</td>
</tr>
<tr align="left" valign="top">
<td id="r3c1" headers="r1c1" align="left" colspan="1" rowspan="1">&#047;<code>l</code>:<em><code>filename</code></em>
</td>
<td headers="r3c1 r1c2" align="left" colspan="1" rowspan="1">Any 
</td>
<td headers="r3c1 r1c3" align="left" colspan="1" rowspan="1"><code>&#047;&#036;ORACLE&#095;HOME&#047;oracm&#047;log&#047;cm.log</code>
</td>
<td headers="r3c1 r1c4" align="left" colspan="1" rowspan="1">Specifies the pathname of the log file for the Cluster Manager. The maximum pathname length is 192 characters. 
</td>
</tr>
<tr align="left" valign="top">
<td id="r4c1" headers="r1c1" align="left" colspan="1" rowspan="1"><code>&#047;?</code>
</td>
<td headers="r4c1 r1c2" align="left" colspan="1" rowspan="1">None
</td>
<td headers="r4c1 r1c3" align="left" colspan="1" rowspan="1">None
</td>
<td headers="r4c1 r1c4" align="left" colspan="1" rowspan="1">Shows help for the arguments of the <code>oracm</code> executable. The Cluster Manager does not start if you specify this argument.
</td>
</tr>
<tr align="left" valign="top">
<td id="r5c1" headers="r1c1" align="left" colspan="1" rowspan="1"><code>&#047;m</code>
</td>
<td headers="r5c1 r1c2" align="left" colspan="1" rowspan="1">Any
</td>
<td headers="r5c1 r1c3" align="left" colspan="1" rowspan="1">25000000
</td>
<td headers="r5c1 r1c4" align="left" colspan="1" rowspan="1">The size of the <code>oracm</code> log file in bytes.
</td>
</tr></tbody>
</table>
</div class="sect2"><a id="i635111" name="i635111"></a>
<div class="sect2">
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<h3>
<font face="arial, helvetica, sans-serif" color="#330099">
Configuring Timing for Cluster Reconfiguration
</font>
</h3>
<p>To avoid database corruption when a node fails, there is a delay before the Oracle9<em>i</em> Real Application Clusters reconfiguration commences. Without this delay, simultaneous access of the same data block by the failed node and the node performing the recovery can cause database corruption. The length of the delay is defined by the sum of the following:
</p>
<ul>
<li type="disc">
<p>Value of the WatchdogTimerMargin parameter
</p>
</li>
<li type="disc">
<p>Value of the WatchdogSafetyMargin parameter
</p>
</li>
<li type="disc">
<p>Value of the Watchdog daemon <code>-m</code> command-line argument
</p>
</li>
</ul>
<div align="center">
<br /><table summary="This is a layout table to format a note" title="This is a layout table to format a note" dir="ltr" border="1" width="80%" frame="hsides" rules="groups" cellpadding="3" cellspacing="0"><tbody>
<tr>
<td align="left" colspan="1" rowspan="1">
<p>
<font face="arial, helvetica, sans-serif">
<strong>See also:</strong>
</font>
</p><a href="#g639928">Table F-2</a> for more information on the WatchdogTimerMargin and WatchdogSafetyMargin parameters, and <a href="#g640035">Table F-1</a> for more information on the Watchdog daemon <code>-m</code> command-line argument.
</td>
</tr></tbody>
</table><br />
</div>
<p>If you use the default values for the Linux kernel soft&#095;margin and Cluster Manager parameters, the time between when the failure is detected and the start of the cluster reconfiguration is 70 seconds. For most workloads this time can be significantly reduced. The following example shows how to decrease the time of the reconfiguration delay from 70 seconds to 20 seconds:
</p>
<ul>
<li type="disc">
<p>Set the value of WatchdogTimerMargin (soft&#095;margin) parameter to 10 seconds.
</p>
</li>
<li type="disc">
<p>Leave the value of the WatchdogSafetyMargin parameter at the default value, 5000ms.
</p>
</li>
<li type="disc">
<p>Leave the value of the Watchdog daemon <code>-m</code> command-line argument at the default value, 5000ms.
</p>
</li>
</ul>
<p>To change the values of the WatchdogTimerMargin (soft&#095;margin) and the WatchdogSafetyMargin:
</p>
<ol type="1" start="1">
<li>
<p>Stop the Oracle instance. 
</p>
</li>
<li>
<p>Reload the <code>softdog</code> module with the new value of soft&#095;margin. For example, enter:
</p>
<pre>&#035;&#047;sbin&#047;insmod softdog soft&#095;margin&#061;10

</pre>
</li>
<li>
<p>Change the value of the WatchdogTimerMargin in the <code>&#036;ORACLE&#095;HOME&#047;oracm&#047;admin&#047;cmcfg.ora</code> file. For example, edit the following line:
</p>
<pre>WatchdogTimerMargin&#061;50000

</pre>
</li>
<li>
<p>Restart <code>watchdogd</code> with the <code>-m</code> command-line argument set to 5000. 
</p>
</li>
<li>
<p>Restart the <code>oracm</code> executable. 
</p>
</li>
<li>
<p>Restart the Oracle instance. 
</p>
</li>
</ol>
</div class="sect2">
</div class="sect1"><a id="i634995" name="i634995"></a>
<div class="sect1">
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<h2>
<font face="arial, helvetica, sans-serif" color="#330099"><a id="sthref785" name="sthref785"></a><a id="sthref786" name="sthref786"></a>Watchdog Daemon and Cluster Manager Starting Options
</font>
</h2>
<p>OCMS supports node fencing by completely resetting the node if an Oracle instance fails and the Cluster Manager thread malfunctions. This approach guarantees that the database is not corrupted. 
</p>
<p>However, it is not always necessary to reset the node if an Oracle instance fails. If the Oracle instance uses synchronous I&#047;O, a node reset is not required. In addition, in some cases where the Oracle instance uses asynchronous I&#047;O, it is not necessary to reset the node, depending on how asynchronous I&#047;O is implemented in the Linux kernel. For a list of certified Linux kernels that do not require node-reset, see the Oracle Technology Network Web site at the following URL:
</p>
<pre>http:&#047;&#047;otn.oracle.com

</pre>
<p>The <code>&#047;a:</code><em><code>action</code></em><code></code> flag in the following command defines OCMS behavior when an Oracle process fails:
</p>
<pre>&#036; oracm &#047;a:&#091;<em>action</em>&#093;

</pre>
<p>In the preceding example, if the <code></code><em><code>action</code></em> argument is set to 0, the node does not reset.By default, the <code>watchdog</code> daemon starts with the <code>-l 1</code> option and the <code>oracm</code> process starts with the <code>&#047;a:0</code> option. With these default values, the node resets only if the oracm or <code>watchdogd</code> process terminates. It does not reset if an Oracle process that can write to the disk terminates. This is safe if you are using a certified Linux kernel that does not require node-reset. 
</p>
<p>In the preceding example, if the <code></code><em><code>action</code></em> argument is set to 1, the node resets if the <code>oracm</code> command, <code>watchdogd</code> daemon, or Oracle process that can write to the disk terminates. In these situations, a SHUTDOWN ABORT command on an Oracle instance resets the node and terminates all Oracle instances that are running on that node.
</p>
</div class="sect1">
</p>
</div>
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