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<b>Oracle9<em>i</em> Administrator's Reference </b>
<br />
<b>Release 2 (9.2.0.1.0) for UNIX Systems: AIX-Based Systems, Compaq Tru64 UNIX, HP 9000 Series HP-UX, Linux Intel, and Sun Solaris</b>
<br />
Part No. A97297-01
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<h1>
<font face="arial, helvetica, sans-serif" color="#330099">C
<br /> Tuning for Oracle9<em>i</em> on Linux
</font>
</h1>
<p>This appendix contains the following tuning information for Oracle9<em>i</em> on Linux:
</p>
<ul>
<li type="disc">
<p><a href="#CHDFFCJB">Extended Buffer Cache Support </a>
</p>
</li>
<li type="disc">
<p><a href="#BABIIHEJ">Asynchronous I/O Support</a>
</p>
</li>
</ul><a id="CHDFFCJB" name="CHDFFCJB"></a>
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<h2>
<font face="arial, helvetica, sans-serif" color="#330099">Extended Buffer Cache Support
</font>
</h2>
<p>Oracle9<em>i</em> can allocate and use more than 4 GB of memory for the database buffer cache. This section describes the limitations and requirements of the extended buffer cache support on Linux.
</p>
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<p>
<font face="arial, helvetica, sans-serif">
<strong>See Also:</strong>
</font>
</p><em>Oracle9i Database Concepts</em> for more information on the extend cache feature.
</td>
</tr></tbody>
</table><br />
<br /><strong><font face="arial, helvetica, sans-serif">In-Memory File System
</font></strong><br />
<p>To use the extended buffer cache support on Linux, create an in-memory file system on the <code>/dev/shm</code> mount point equal in size or larger than the amount of memory that you intend to use for the database buffer cache.
</p>
<p>For example, for Linux to create an 8 GB <code>shmfs</code> file system on the <code>/dev/shm</code> mount point, enter the following as the <code>root</code> user:
</p>
<pre>$ mount -t shm shmfs -o size=8g /dev/shm
</pre>
<p>When Oracle9<em>i</em> starts with the extended buffer cache feature enabled, it creates a file in the <code>/dev/shm</code> directory that corresponds to the Oracle buffer cache.
</p>
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<p>
<font face="arial, helvetica, sans-serif">
<strong>Note:</strong>
</font>
</p>If an in-memory file system is already mounted on the <code>/dev/shm</code> mount point, ensure that it is equal to or larger than the amount of memory that is used for the database buffer cache.
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<br /><strong><font face="arial, helvetica, sans-serif">USE_INDIRECT_DATA_BUFFERS Parameter
</font></strong><br />
<p>To enable the extended buffer cache feature, set the USE_INDIRECT_DATA_BUFFERS parameter to <code>true</code> in the <code>init</code><em><code>sid</code></em>.<code>ora</code> file. Doing this allows Oracle9<em>i</em> to specify a larger buffer cache.
</p>
<br /><strong><font face="arial, helvetica, sans-serif">Dynamic Cache Parameters
</font></strong><br />
<p>Do not use the following dynamic cache parameters while the extended cache feature is enabled:
</p>
<ul>
<li type="disc">
<p>DB_CACHE_SIZE
</p>
</li>
<li type="disc">
<p>DB_2K_CACHE_SIZE
</p>
</li>
<li type="disc">
<p>DB_4K_CACHE_SIZE
</p>
</li>
<li type="disc">
<p>DB_8K_CACHE_SIZE
</p>
</li>
<li type="disc">
<p>DB_16K_CACHE_SIZE
</p>
</li>
<li type="disc">
<p>DB_32K_CACHE_SIZE
</p>
</li>
</ul>
<p>If the extended cache feature is enabled, use the DB_BLOCK_BUFFERS parameter to specify the database cache size.
</p>
<br /><strong><font face="arial, helvetica, sans-serif">Limitations
</font></strong><br />
<p>The following limitations apply to the extended buffer cache feature on Linux:
</p>
<ul>
<li type="disc">
<p>You cannot change the size of the buffer cache while the instance is running.
</p>
</li>
<li type="disc">
<p>You cannot create or use tablespaces with non-standard block sizes.
</p>
</li>
</ul>
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<p>
<font face="arial, helvetica, sans-serif">
<strong>See Also:</strong>
</font>
</p><em>Oracle9i SQL Reference</em> for information on the standard block size used by the CREATE TABLE SPACE command.
</td>
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</table><br />
</div class="sect1"><a id="BABIIHEJ" name="BABIIHEJ"></a>
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<h2>
<font face="arial, helvetica, sans-serif" color="#330099">Asynchronous I/O Support
</font>
</h2>
<p>Oracle9<em>i</em> supports kernel asynchronous I/O. This feature is disabled by default. If you are running Oracle9<em>i</em> on a system that supports kernel asynchronous I/O and that is certified by Oracle Corporation to use asynchronous I/O, perform the following steps to enable asynchronous I/O support:
</p>
<ol type="1" start="1">
<li>
<p>As the <code>root</code> user, change directory to the <code>$ORACLE_HOME/rdbms/lib</code> directory.
</p>
</li>
<li>
<p>Enter the following commands:
</p>
<pre>$ make -f ins_rdbms.mk async_on
</pre>
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<p>
<font face="arial, helvetica, sans-serif">
<strong>Note:</strong>
</font>
</p>If you receive the <code>"/usr/bin/ld: cannot find -laio"</code> error, then the system does not support kernel asynchronous I/O and you must enter the following command to restore the Oracle instance to a usable state:
<p><code>$ make -f ins_rdbms.mk async_off</code>
</p>
</td>
</tr></tbody>
</table><br />
</div>
</li>
</ol>
<p>By default, the DISK_ASYNCH_IO parameter in the <code>init</code><em><code>sid</code></em><code>.ora</code> file is set to <code>true</code> to enable asynchronous I/O on raw devices. To enable asynchronous I/O on filesystem files:
</p>
<ol type="1" start="1">
<li>
<p>Ensure that all Oracle data files are located on file systems that support asynchronous I/O.
</p>
</li>
<li>
<p> Set the FILESYTEMIO_OPTIONS parameter in the <code>init</code><em><code>sid</code></em><code>.ora</code> file to <code>asynch</code>.
</p>
</li>
</ol>
</div class="sect1">
</p>
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