A data slice is an optimization feature that helps direct queries to the data of the appropriate partitions. A data slice is not a substitute for, nor an alternative to, the source specification for the partition. That is, a data slice cannot be used to limit the data selected from the partition's fact table and included in the partition. Data slices are applicable only to objects that use the ROLAP storage mode. You can specify a data slice when you create a partition using the Partition Wizard.
A data slice of a partition should reflect, as closely as possible, the data in the partition. For example, if a partition is limited to 2004 data, the partition's data slice should specify the 2004 member of the Time dimension. It is not always possible to specify a data slice that reflects the exact contents of a partition. For example, if a partition contains data for only January and February, but the levels of the Time dimension are Year, Quarter, and Month, the Partition Wizard cannot select both the January and February members. In such cases, select the parent of the members that reflect the partition's contents. In this example, select Quarter 1.