There are 4 tiers –  Client tier - The Infosphere Information Server client tier is used for computer development and full management through client programs and consoles.  Services tier - The services layer is used to provide standard services such as metadata and logging, as well as other engine-specific services. This includes application servers, various product modules, and other product services.  Engine tier - The engine tier consists of a set of logical components used to run the jobs and other tasks of the product modules.  Metadata Repository tier - The metadata repository tier includes the metadata repository, the analytics database, and the computer. Used to share metadata, shared data, and configuration information.