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<h1>NonFlushingStorage</h1>
<p>NonFlushingStorage is a special IO <span class="MCPopup"><a href="javascript:void(0);" class="MCPopupSpot" onclick="FMCPopup( event, this ); return false;" MadCap:src="../storage.htm">Storage<img style="border: none;margin-left: 5px;" src="../../../SkinSupport/ExpandingClosed.gif" MadCap:altsrc="../../../SkinSupport/ExpandingOpen.gif" class="MCExpandingIcon" onload="if ( typeof( FMCPreloadImage ) == 'function' ) { FMCPreloadImage( '../../../SkinSupport/ExpandingOpen.gif' ); }" /></a></span>, which can be used to
improve commit performance. Committing is a complex operation and requires
flushing
to the hard drive after each stage of commit. This is necessary as
most operating system try to avoid the overhead of disk access by
caching disk write data and only flushing the resulting changes to the
disk. In the case of db4o commit it would mean that the physical write
of some commit stages will be partially skipped and the data will be
irreversibly lost. </p>
<p>However,
physical access to the hard drive is a time-consuming operation and may
considerably affect the performance. That is where
NonFlushingStorage comes in: it allows the operating system to keep
commit data in cache and do the physical writes in a most performant
order. This may sound very nice, but in fact a system shutdown while
the commit data is still in cache will lead to the database corruption.</p>
<p>The following example shows how to use the NonFlushingStorage. You
can run it and see the performance improvement on commit stage.</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IEmbeddedConfiguration configuration = Db4oEmbedded.NewConfiguration();
IStorage fileStorage = new FileStorage();
// the non-flushing storage improves performance, but risks database corruption.
IStorage cachingStorage = new NonFlushingStorage(fileStorage);
configuration.File.Storage = cachingStorage;
IObjectContainer container = Db4oEmbedded.OpenFile(configuration, "database.db4o");</pre>
<div class="codesnippet-meta">IOConfigurationExamples.cs: Using the non-flushing storage
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<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim configuration As IEmbeddedConfiguration = Db4oEmbedded.NewConfiguration()
Dim fileStorage As IStorage = New FileStorage()
' the non-flushing storage improves performance, but risks database corruption.
Dim cachingStorage As IStorage = New NonFlushingStorage(FileStorage)
configuration.File.Storage = cachingStorage
Dim container As IObjectContainer = Db4oEmbedded.OpenFile(Configuration, "database.db4o")</pre>
<div class="codesnippet-meta">IOConfigurationExamples.vb: Using the non-flushing storage
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<p>Please, remember, that NonFlushingStorage is potentially dangerous
and any unexpected system shutdown may corrupt your database. Use with
caution and avoid using in production environments. </p>
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