Adding Currency Conversion - Expert Cube Development with SSAS Multidimensional Models - page 201

• When a user queries a cube with Writeback enabled, the Writeback partition

has to be queried along with the original partitions. Using MOLAP storage
mode for your Writeback partition, which is the default, reduces this
performance penalty and we recommend you always do this rather than
use ROLAP storage. However, using MOLAP storage means committing
updated cell values will take slightly longer because Analysis Services now
has to process the Writeback partition as well.

If you intend to use Writeback, first check whether your
chosen client tool supports it. Some, for example Excel 2007,
do not (it is supported in Excel 2010 and following versions).

Summary
In this chapter, we have seen how to implement currency conversion in several
different ways. In many cases currency conversion can take place in the ETL phase
and where this is possible it is the best option to take. However, there are some
situations that require that currency conversion be implemented in Analysis Services.

We have seen how to use the Define Currency Conversion option in the Add
Business Intelligence wizard. This wizard generates the necessary objects and MDX
Script calculations to implement currency conversion in both the Standard and
Enterprise editions of Analysis Services. For better query performance, we have also
discussed how to implement currency conversion using the MeasureExpression
property instead, which is available only in Enterprise edition.

In the next chapter, we will discuss tools and techniques to improve query performance.