Tuesday, 29 April 2014

Unified Dimensional Model in SSAS

UDM (Unified Dimensional Model)

             The UDM is central to your Analysis Services database architecture.UDM is your friend because it helps you narrow the gap between end users and data they need. Analysis Services provides you with features that help you design a model that will serve the needs of end users. It provides you with a way to bring data from multiple heterogeneous sources into single model.

              Pre-UDM versions of Analysis Services only supported one fact table per cube. Therefore, only one data source could be used for specifying the fact table of cube.


Figure: The UDM provides a bridge between end users and their data

                  The above figure shows the architecture of the Unified Dimensional Model that is implemented in Analysis Services. It helps you to integrate data from various data sources such as Oracle, Sql Server, DB2 and TeraData into a single model that merges the underlying schemas into a single schema.To restrict end user view by using concept Perspectives in Analysis Services.
                  In OLAP, the data analyzed by end users is often historical data that might be a few days, months, or even year old. XML for Analysis (XMLA) standard, which allows client tools to retrieve data from Analysis Services. To write OLAP queries retrieve data within a few seconds.

The UDM consists of several components as follows
    • Data source – It represents a connection to the database where the data is stored.
    • Data source view (DSV) - Abstracts the underlying database schema. Although a DSV might seen redundant, it can be very useful by letting you augment the schema.
    • Dimensional Model – After you’ve created a DSV, the next step is to build the dimensional model.

Key elements of the UDM are as follows:
    • Heterogeneous data access support: UDM helps you to integrate and encapsulate data from heterogeneous data sources. It helps you combine various schemas into a single model.
    • Real time data access with high performance: The UDM provides end users with real time data access.     The UDM creates a MOLAP cache of underlying data. It helps in providing real time data access with     the speed of an OLAP database due to MOLAP cache.
    • Rich metadata, ease of use for exploration, and navigation of Data: UDM provides a consolidated view of the underlying data sources with the richness of metadata provided by the OLAP world. End users are able to exploit this Meta data to navigate and explore data in support of marking business decisions.
    • Rich analytics support: UDM provides rich analytics such as Key performance Indicators and Actions that help in understanding your business with ease and automatically take appropriate actions based on changes in data by using MDX (Multidimensional expressions) language.
    • Model for Reporting and Analysis: It provides you with the capability of not only querying the aggregated data that are typically used for analysis, but also has the ability to provide for detailed reporting up to the transaction level across multiple heterogeneous data sources.


Additional Features in Analysis services 2008:
    • In Analysis services 2008, the UDM is tightly integrated with data mining features. You can also create a data mining dimension from data mining model.


      • Several MDX functions are also added in Analysis services 2008.
      • In a dimension that can have hundreds of attributes. But in real time attributes with in dimension are not used in many queries. Only a subset of the attributes might be heavily used. Including unnecessary attributes and hierarchies in your UDM cases performance decreases in some cases.
             The Analysis Services 2008 design tools also allow you to better visualize the relationships between the attributes that you need and help you build a better dimension model. (It’s known as Fine Tuning Dimensions.)

             Merge UDM in Analysis Services 2008 is become a powerful, enterprise class product that you can use to build large scale OLAP databases and implement strategic business analysis applications against those databases.

             Finally you learn about the overall architecture of Analysis Services 2008 followed by the concept of the unified Dimensional Model (UDM), it helps you to have a unified view of your entire Datawarehouse.

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