A logical partition (LPAR) is the division of a computer's processor s, memory , and storage into multiple sets of resources so that each set of resources can be operated independently with its own operating system instance and application s. The number of logical partitions that can be created depends on the system's processor model and resources available. Typically, partitions are used for different purposes such as database operation or client/server operation or to separate test and production environments. Each partition can communicate with the other partitions as if the other partition is in a separate machine. Logical partitioning was first studied by IBM in 1976 and later introduced by Amdahl and then IBM. Hitachi and Sun Microsystems also use forms of logical partitioning. Today, both IBM's S/390 (now z/900 Series) and AS/400 products support logical partitioning.