Surrogate Key Generator stage

The Surrogate Key Generator stage is a processing stage that generates surrogate key columns and maintains the key source.

A surrogate key is a unique primary key that is not derived from the data that it represents, therefore changes to the data will not change the primary key. In a star schema database, surrogate keys are used to join a fact table to a dimension table.

The Surrogate Key Generator stage can have a single input link, a single output link, both an input link and an output link, or no links. Job design depends on the purpose of the stage.

You can use a Surrogate Key Generator stage to perform the following tasks:

• Create or delete the key source before other jobs run
• Update a state file with a range of key values
• Generate surrogate key columns and pass them to the next stage in the job
• View the contents of the state file

Generated keys are unsigned 64-bit integers. The key source can be a state file or a database sequence. If you are using a database sequence, the sequence must be created by the Surrogate Key stage. You cannot use a sequence previously created outside of DataStage.

You can use the Surrogate Key Generator stage to update a state file, but not a database sequence. Sequences must be modified with database tools.