Getting the best possible query performance out of a SAP Business Intelligence system is one of the main responsibilities of a BI consultant. Optimizing data models (e.g. remodeling and creating indexes) is one of the activities you could perform in order to achieve this. In some cases optimizing is not sufficient. Partioning data objects is sometimes forgotten, but might do the trick.
Partitioning data objects is a piece of cake from SAP BW 7.3 onwards (see attachment). However, when running an old version of SAP BW with a DB2 database, this could only be achieved by using multi-dimensional clustering (MDC). This feature, which is only applicable for DB2 databases, allows you to physically cluster data in a table along multiple dimensions. It is especially beneficial for query performance in business intelligence applications that use star and snowflake schemas and process large amounts of data with restrictions on several dimensions.
If you have tried almost everything to optimize your query performance then MDC could be your last option. In the end upgrading SAP BW to a higher version (which makes is possible to create semantic partitioned objects) and using an accelerator (like the BWA or HANA) will be more beneficial for the long term.