BPAM meaning in Computing ?

In IBM mainframe operating systems, basic partitioned access method (BPAM) is an access method for libraries, called partitioned datasets (PDSes) in IBM terminology. BPAM is used in OS/360, OS/VS2, MVS, z/OS, and others.

A PDS consists of members (internally identical to sequential data sets), registered in a list called the directory. The combination of members and directory is a single dataset on disk. The directory contains a list of member's names (8 characters, padded on the right with blanks, as required) and member's addresses. Addresses are relative to the start of the dataset in order to allow the PDS to be moved to a different disk location.

Partitioned datasets can store any type of data, but they are often used to store executable programs, or load modules, sometimes called binaries in other systems. Other uses include system assembler macro definitions, job control procedures, and program source code.