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<th colspan="3" align="center">The DB_CONFIG File</th>
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<th width="60%" align="center">Chapter 3. Configuring the Berkeley DB SQL interface</th>
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<h2 class="title" style="clear: both"><a id="using_dbconfig"></a>The DB_CONFIG File</h2>
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<div class="toc">
<dl>
<dt>
<span class="sect2">
<a href="using_dbconfig.html#dbconfigcreate">Creating the DB_CONFIG File Before Environment Creation</a>
</span>
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<dt>
<span class="sect2">
<a href="using_dbconfig.html#envrecreate">Re-creating the Environment</a>
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<p>
You can configure most aspects of your Berkeley DB environment by
using the <code class="literal">DB_CONFIG</code> file. This file must be
placed in your environment directory. When using the BDB SQL interface, this is
the directory created alongside of your database. It has
the same name as your database, followed by a
<code class="literal">-journal</code> extension. For example, if your
database is named <code class="literal">mydb.db</code>, then your
environment directory is created next to the
<code class="literal">mydb.db</code> file, and it
is called <code class="literal">mydb.db-journal</code>.
</p>
<p>
If a <code class="literal">DB_CONFIG</code> file exists in your
environment directory, it will be read for lines of the
format <span class="bold"><strong>NAME VALUE</strong></span> when
your environment is opened. This happens when your
application starts up and creates its first connection to
the database.
</p>
<p>
One or more whitespace characters are used to delimit the two parts of
the line, and trailing whitespace characters are discarded. All empty
lines or lines whose first character is a whitespace or hash
(<span class="bold"><strong>#</strong></span>) character are ignored. Each
line must specify both the NAME and the VALUE of the pair. The
specific NAME VALUE pairs you can use with the BDB SQL interface are
documented in the <a class="ulink" href="http://download.oracle.com/docs/cd/E17076_02/html/api_reference/C/BDB-C_APIReference.pdf" target="_top"> Berkeley DB C API
</a>.
</p>
<p>
In some cases, you must either specify a configuration
option before the environment is created, or the
environment must be re-created before the configuration
option will take effect. The documentation for each
configuration option will indicate where this is true.
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="dbconfigcreate"></a>Creating the DB_CONFIG File Before Environment Creation</h3>
</div>
</div>
</div>
<p>
In order to provide the <code class="literal">DB_CONFIG</code> file before
the environment is first created, physically make the
environment directory in the correct location in your
filesystem (this is wherever you want to place your
database file), and put the <code class="literal">DB_CONFIG</code>
file there before you create your database.
</p>
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<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="envrecreate"></a>Re-creating the Environment</h3>
</div>
</div>
</div>
<p>
Some <code class="literal">DB_CONFIG</code> parameters require you to
re-create your environment before they take effect.
The <code class="literal">DB_CONFIG</code> parameter descriptions
indicates where this is the case.
</p>
<p>
To re-create your environment:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
Make sure the <code class="literal">DB_CONFIG</code> file
contains the following line:
</p>
<pre class="programlisting">add_data_dir ..</pre>
<p>
(This line should already be in the
<code class="literal">DB_CONFIG</code> file.)
</p>
</li>
<li>
<p>
Run the <a href="../api_reference/C/db_recover.html" class="olink">db_recover</a> command line utility. If
you run it from within your environment
(<code class="literal">-journal</code>) directory, no
command line arguments are required. If you run
it from outside your environment directory, use
the <code class="literal">-h</code> parameter to identify
the location of the environment:
</p>
<pre class="programlisting">db_recover -h /some/path/to/mydb.db-journal</pre>
</li>
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