How Many Partitions Per Measure Group Are Allowed in SSAS Standard Edition?

Reposted from Chris Webb's blog with the author's permission.

Most people know that the ability to partition a measure group is a feature of Analysis Services Multidimensional Enterprise Edition, but that doesn't mean that in Standard Edition you are limited to just having one partition per measure group. In fact it is possible to use up to three partitions per measure group in SSAS Multidimensional SE, with some limitations. For a long time I wasn't sure whether this was legal, as opposed to possible, according to the terms of the SQL Server licence but since this page in Books Online (thanks to Rob Kerr for the link) states that you can have up to three partitions in SE then I assume it is:

http://msdn.microsoft.com/en-us/library/cc645993(v=SQL.110).aspx#BISemModel_multi

HOWEVER

If you do decide to use more than one partition in SSAS SE then you do need to understand the risks involved - and the reason I wanted to write this post is because I see a lot of people using more than one partition per measure group in SE without understanding those risks. Strictly speaking, SE is only designed to work with one partition per measure group. It needs those extra two partitions for two pieces of functionality:

1. To support writeback, because using this feature requires SSAS to create a separate partition to hold writeback values
2. To support incremental processing, because when you do incremental processing on a partition in the background SSAS needs to create a new partition, process it and then merge it with your existing partition

Therefore if you create more than one partition per measure group in SE you may find that writeback and/or incremental processing will break.

Chris has been working with Microsoft BI tools since he started using beta 3 of OLAP Services back in the late 90s. Since then he has worked with Analysis Services in a number of roles (including three years spent with Microsoft Consulting Services) and he is now an independent consultant specialising in complex MDX, Analysis Services cube design and Analysis Services query performance problems. His company website can be found at http://www.crossjoin.co.uk and his blog can be found at http://cwebbbi.wordpress.com/ .