You will see this or a similar code sample when referring to clearing the analysis services cache. However, I have yet to find a good resource that explains exactly what running an empty MDX query against a cube really is doing.
Here is an example of code to clear the cache:
<Batch xmlns="http://schemas.microsoft.com/analysisservices/2003/engine">
<ClearCache>
<Object>
<DatabaseID>Adventure Works DW</DatabaseID>
</Object>
</ClearCache>
</Batch>
GO
SELECT {} ON 0
FROM [Adventure Works]
From what I have gathered (mainly due to feedback received from Darren Gosbell, http://geekswithblogs.net/darrengosbell/Default.aspx) is that running the empty MDX query on a cube essentially reloads in cache all of the calculated measures, named sets, scoping, etc... which have been setup and defined in the cube. This does not cache any data.
If anyone has a good resource or additional information, I'd love to hear about it.
