QSAM : Queued Sequential Access Method : A file access method for reading, writing and updating sequential data sets and partitioned data set members.
BSAM : Basic Sequential Access Method
BDAM : Basic Direct Access Method
ISAM : Indexed Sequential Access Method : A method for managing how a computer accesses records and files stored on a hard disk. While storing data sequentially, ISAM provides direct access to specific records through an index. This combination results in quick data access regardless of whether records are being accessed sequentially or randomly.
BPAM : Basic Partitioned Access Method : An access method for reading members of partitioned data sets.