Updating olap dimensions
Hierarchy versioning is not enabled by default for Type 2 SCDs.Thus, when you create a Type 2 SCD using the Create Dimension Wizard, hierarchy versioning is disabled.When you use the wizard to create a Type 2 SCD or a Type 3 SCD, Oracle Warehouse Builder creates the required additional attributes. When the value of a triggering attribute changes, the current record is closed.A new record is created with the changed data values and this new record becomes the current record.
A dimension consists of a set of levels and a set of hierarchies defined over these levels.Use Type 2 and Type 3 SCDs to store and manage both current and historical data over time in a data warehouse.Type 1 dimensions, referred to as dimensions, do not preserve historical data.The current record is the one with a null or the previously specified value in the expiration date.All the levels in a dimension need not store historical data. To define a Type 2 Slowly Changing Dimension (SCD), you must identify the following: Each version of a record is assigned a different surrogate identifier.