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<th colspan="3" align="center">Removing Log Files</th>
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<td width="20%" align="left"><a accesskey="p" href="hotfailover.html">Prev</a> </td>
<th width="60%" align="center">Chapter 5. Managing DB Files</th>
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<div>
<h2 class="title" style="clear: both"><a id="logfileremoval"></a>Removing Log Files</h2>
</div>
</div>
</div>
<p>
By default DB does not delete log files for you. For this reason,
DB's log files will eventually grow to consume an
unnecessarily large amount of disk space. To guard against
this, you should periodically take administrative action to
remove log files that are no longer in use by your application.
</p>
<p>
You can remove a log file if all of the following are true:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
the log file is not involved in an active transaction.
</p>
</li>
<li>
<p>
a checkpoint has been performed
<span class="emphasis"><em>after</em></span> the log file was
created.
</p>
</li>
<li>
<p>
the log file is not the only log file in the
environment.
</p>
</li>
<li>
<p>
the log file that you want to remove has already been
included in an offline or hot backup.
Failure to observe this last condition can cause your
backups to be unusable.
</p>
</li>
</ul>
</div>
<p>
DB provides several mechanisms to remove log files that
meet all but the last criteria (DB has no way to know which
log files have already been included in a backup). The
following mechanisms make it easy to remove unneeded log files,
but can result in an unusable backup if the log files are not first
saved to your archive location. All of the following
mechanisms automatically delete unneeded log files for you:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
Run the <span class="command"><strong>db_archive</strong></span> command line
utility with the <code class="literal">-d</code> option.
</p>
</li>
<li>
<p>
From within your application, call the
<span>
<code class="methodname">Environment.removeOldLogFiles()</code>
method.
</span>
</p>
</li>
<li>
<p>
<span>
Specify <code class="literal">true</code> to the
<code class="methodname">EnvironmentConfig.setLogAutoRemove()</code>
method. Note that setting this property affects
all environment handles opened against the
environment; not just the handle used to set
the property.
</span>
</p>
<p>
Note that unlike the other log removal mechanisms
identified here, this method actually causes log files
to be removed on an on-going basis as they become
unnecessary. This is extremely desirable behavior if
what you want is to use the absolute minimum amount of
disk space possible for your application. This
mechanism <span class="emphasis"><em>will</em></span> leave you with
the log files that are required to run normal recovery.
However, it is highly likely that this mechanism will
prevent you from running catastrophic recovery.
</p>
<p>
Do NOT use this mechanism if you want to be able to
perform catastrophic recovery, or if you want to be
able to maintain a hot backup.
</p>
</li>
</ul>
</div>
<p>
In order to safely remove log files and still be able to
perform catastrophic recovery, use the
<span class="command"><strong>db_archive</strong></span> command line utility as follows:
</p>
<div class="orderedlist">
<ol type="1">
<li>
<p>
Run either a normal or hot backup as described in
<a class="xref" href="backuprestore.html" title="Backup Procedures">Backup Procedures</a>. Make
sure that all of this data is safely stored to your
backup media before continuing.
</p>
</li>
<li>
<p>
If you have not already done so, perform a checkpoint.
See <a class="xref" href="filemanagement.html#checkpoints" title="Checkpoints">Checkpoints</a>
for more information.
</p>
</li>
<li>
<p>
If you are maintaining a hot backup, perform the hot
backup procedure as described in
<a class="xref" href="hotfailover.html" title="Using Hot Failovers">Using Hot Failovers</a>.
</p>
</li>
<li>
<p>
Run the <span class="command"><strong>db_archive</strong></span> command line
utility with the <code class="literal">-d</code> option against
your production environment.
</p>
</li>
<li>
<p>
Run the <span class="command"><strong>db_archive</strong></span> command line
utility with the <code class="literal">-d</code> option against
your failover environment, if you are maintaining one.
</p>
</li>
</ol>
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