Chapter 9

Microsoft SQL Server OLAP Services

Review Questions

1. What is the overall purpose of OLAP Services?

To store data in multidimensional cubes that contain precalculated values. This speeds up queries against the data.

2. How is OLAP different from data warehousing?

Data warehousing is the technology of moving enterprise data into one database, often with some summarization. OLAP is the technology to summarize data into multidimensional structures that allow you to retrieve data quickly.

3. What are the possible cube storage methods?

Cubes can be stored in multidimensional structures (MOLAP), relational tables (ROLAP), or a combination of the two (HOLAP).

4. What is the difference between designing storage and processing a cube?

Designing storage selects aggregations and storage types. Processing creates the selected aggregations on the selected storage type.

5. How much programming must you do to set up cubes?

None. But OLAP Services has Decision Support Objects that allow programmatic access if you are a programmer.

6. What is the difference between NT Groups and OLAP Roles?

NT Groups are maintained by the operating system. OLAP Roles are maintained by OLAP Services. OLAP Roles receive access rights to cubes. NT Groups are placed in OLAP Roles.

7. What is the best way to decide on aggregations for your cube?

Let the wizard decide. After the cube is used for a while, the aggregations can be further optimized.

8. When would you process, refresh, or incrementally update your cubes?

Process a cube when the cube is new or when the structure of a cube has changed.

Update incrementally when new data has been added to the warehouse but existing data did not change.

Refresh data if the underlying base data has changed.