Surrogate keys are a great way to start an argument on a data warehouse project. Surrogate Key is a unique identification key. To be precise Surrogate Key is a Primary Key for a Dimension table.It is alternative to natural key . And in natural key, it may have alphanumeric composite key but the surrogate is always single numeric key. Surrogate key is used to generate key columns, for which characteristics can be specified. The surrogate key generates sequential incremental and unique integers for a provided start point. It can have a single input and a single output link. Most importance of using it is it is independent of underlying database. i.e Surrogate Key is not affected by the changes going on with a database.
A detailed discussion on InfoSphere DataStage Surrogate Key