Database Reference
In-Depth Information
Figure 3.44
Selecting the XOLAP model.
3. Calculation: Calculations (member formulae) in xoLAP models are handled
by the Essbase calculation engine. As such, complex calculations that are often
more difficult relationally can be handled in the oLAP engine.
The main downside (aside from the design restrictions) is performance. With an
xoLAP, model performance is no longer governed by Essbase, but rather the underly-
ing data sources. If the source system is slow to respond, so is Essbase. Further, you can-
not generate custom SQL when working with xoLAP, you have to use the generic SQL
generated by Studio. In short, xoLAP models are very often significantly slower than
full oLAP models.
Although performance concerns must be considered, from a prototyping perspec-
tive, xoLAP models provide an excellent vehicle for data exploration in the source sys-
tems. Because xoLAP models deployments are metadata only, they are extremely fast
(comparatively) to deploy. you can then use an xoLAP model to walk through the data-
set with the client or key stakeholders and validate assumptions about the source data.
to build an xoLAP model from Studio, you need to select the following Essbase
properties for cube schema:
• Aggregate Storage model
• Duplicate member name Support
• xoLAP model
Note:
When you select xoLAP model, as in Figure 3.44, the other two options are
automatically selected and “grayed out” because they are not optional for xoLAP.
In addition to the Essbase property requirements, there are hierarchy/dimension
design restrictions when working with xoLAP:
• Derived text measures cannot be used. no hierarchies allowed in attribute
dimensions.
• recursive tables for hierarchy definition are not allowed.
• hierarchical measures are not allowed.
• Level 0 user-defined members are not allowed.
• Filters cannot be used on the hierarchies used in the model.
3.7.4 Managing Studio Processes
given that Studio is a front end for Essbase, it is easy to forget that under the hood,
Studio is a server. It is a stand-alone engine that performs modeling tasks directly on
data sources and communicates with and deploys models to the Essbase server. As such,
the Studio server has a series of settings you can manage and monitor for troubleshoot-
ing purposes. These settings center on how Studio handles parallel processes and how
the server handles thread usage.
