Partitions

A partition is a data structure that holds some or all of the data in a measure group. Every measure group is divided into partitions. A partition defines a subset of the fact data that is loaded into the measure group. SSAS Standard Edition allows only one partition per measure group, while SSAS Enterprise Edition allows a measure group to contain multiple partitions.

Partitions are a feature that is transparent to the end user, but they have a major impact on both the performance and the scalability of OLAP cubes. All partitions for a measure group always exist in the same physical database.

Partitions make it possible for an administrator to better manage an OLAP cube and improve an OLAP cube’s performance. For example, you can remove or reprocess the data in one partition of a measure group without affecting the rest of the measure group. When you load new data into a fact table, only the partitions that should contain the new data are affected.

Partitioning also improves processing and query performance for OLAP cubes. SSAS can process multiple partitions in parallel, leading to a much more efficient use of CPU and memory resources on the server. While it runs a query, SSAS fetches, processes, and aggregates data from multiple partitions as well. Only partitions that contain the data that is relevant to a query are scanned, which reduces the overall amount of input and output.

One example of a partitioning strategy is to place the fact data for each month into a monthly partition. At the end of each month, all the new data goes into a new partition, which leads to a natural distribution of data with nonoverlapping values.

Use the Measure Groups pane on the Partitions tab in Cube Designer to manage the partitions associated with each measure group in the cube.

Partitions

Displays a grid containing the list of partitions that support the selected measure group. The grid contains the following columns:

(Ordinal) : Displays the ordinal position of the partition within the measure group.

Click to select the entire row for the partition.

Partition Name:Type the name of the selected partition.

Source: Type the table name (for table binding) or query (for query binding) that provides the fact table data for the selected partition.

Click the ... button to display the Partition Source dialog box and define the source for the selected partition.