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<h1>Allow Version Updates</h1>
<p>The db4o database file format is a subject to change to
allow progress for performance and additional features.
db4o does not support downgrades back to previous versions of database files.
In order to prevent accidental upgrades when using different db4o versions, db4o does not upgrade databases by default.
Database upgrading can be turned on with the following configuration switch: </p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IEmbeddedConfiguration configuration = Db4oEmbedded.NewConfiguration();
configuration.Common.AllowVersionUpdates = true;
// reopen and close the database to do the update
IObjectContainer container = Db4oEmbedded.OpenFile(configuration, DatabaseFile);
container.Close();</pre>
<div class="codesnippet-meta">CommonConfigurationExamples.cs: Update the database-format
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<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim configuration As IEmbeddedConfiguration = Db4oEmbedded.NewConfiguration()
configuration.Common.AllowVersionUpdates = True
' reopen and close the database to do the update
Dim container As IObjectContainer = Db4oEmbedded.OpenFile(configuration, DatabaseFile)
container.Close()</pre>
<div class="codesnippet-meta">CommonConfigurationExamples.vb: Update the database-format
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<p style="mc-redacted: none;">Please note that, once the database file version is updated, there is no way to
get back to the older version.
When a database file is opened successfully with the new db4o version, the
upgrade of the file will take place automatically. You can simply upgrade
database files by opening and closing a db4o database once. <![CDATA[ ]]></p>Recommendations for upgrading: <ul><li value="1">Backup your database file to be able to switch back. </li><li value="2"><a href="../../advanced_topics/defragment.htm">Defragmenting</a> a database file with the new db4o version
after upgrading can make the database more efficient.
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