Standard Format

During creation of a sequential data set (to be processed by BSAM or QSAM) with fixed-length records, the RECFM subparameter of the DCB macro can specify a standard format (RECFM=FS or FBS). A sequential data set with standard format records (format-FS or -FBS) sometimes can be read more efficiently than a data set with format-F or -FB records. This efficiency is possible because the system is able to determine the address of each record to be read, because each track contains the same number of blocks.

A standard-format data set must conform to the following specifications:

All records in the data set are format-F records.
No block except the last block is truncated. (With BSAM, you must ensure that this specification is met.) If the last block is truncated, the system writes it where a full size block would have been written.
Every track except the last contains the same number of blocks.
Every track except the last is filled as determined by the track capacity formula established for the device.
The data set organization is physically sequential. You cannot use format-FS for a PDS or PDSE.