Selection of an Access Method

In selecting an access method for a data set, consider the organization of the data set, what you need to specify through macros, and the device type:

VSAM data sets, PDSEs, PDSs, extended-format data sets, direct data sets, and UNIX files must be stored on DASD volumes.
Sequential data sets can be on DASD or tape volumes, or these data sets can be read from or written to a unit record device or TSO/E terminal. They can be spooled data sets. Spooled data sets named SYSOUT can be directed over a network. Sequential data sets also can be dummy data sets.

In addition, you should select a data organization according to the type of processing you want to do: sequential or direct. For example, RRDSs or key-sequenced data sets are best for applications that use only direct access, or both direct and sequential access. Sequential or VSAM entry-sequenced data sets are best for batch processing applications and for sequential access.

Restriction: You cannot process VSAM data sets with non-VSAM access methods, although you can use DIV macros to access linear data sets. You cannot process non-VSAM data sets except for UNIX files with VSAM.

See z/OS TSO/E Command Reference for information about using BSAM and QSAM to read from and write to a TSO/E terminal in line mode.