What are the files used for ssas storage

Question

Please help me to understand about the files used for storage in ssas.I know some basics about ROLAP,HOLAP,etc.I want to know about the kind of files ssas is creating and using for storing data for these ROLAP,HOLAP,MOLAP methods.(For example in normal sql database we know .mdf file and this file is logicaly divided into 8kb files,their the data is storing in row wise..etc).

Thanks in advance..

Answer 1

SSAS storage is quite different from the DBEngine. With MOLAP, the data is spread out across many files which makes sense when you consider the typical access patterns for OLAP queries (read: random access) where as OLTP queries are typically more sequential in nature.

If you look in the DATA directory of your SSAS instance, you'll see a folder for each AS-database. Inside, you have separate folders for each object in your cube (dimensions, measure groups, etc). This is why it makes sense to put DistinctCount measures in there own measure groups.

Inside the dimension folders you will see a separate set of files for each attribute. The set consists of a variety of file types depending on the design. Are their attribute relationships defined in addition to the default key? What about aggregations? User Hierarchies?

The measure groups are a little more straight forward. There's a separate file for each partition that contains the actual facts/data. Everything else is related to the aggregations (linking dimension files to fact files).

For detailed information on file types and physical storage, check this book out... Microsoft SQL Server 2005 Analysis Services