Physical sequential data sets and OSAM

Overflow sequential access method (OSAM) requires all data blocks, including the last one, to be the same length. DFSMShsm can manage data sets processed with OSAM when the DSORG field specifies PS (hereafter called PS/OSAM) if the PS/OSAM data sets are not reblocked.

Note: If this restriction is inadvertently bypassed, the data is not lost but can be addressed by OSAM after the data is returned to its original format.

If reblocking occurs, the last data block may be short. Therefore, the user must ensure that data can be addressed in PS/OSAM data sets by making certain that DFSMShsm does not reblock them.

If reblocking of a PS/OSAM data set occurs, a separate job must be run to return the data set to its original block size. The DFSMShsm data set reblock exit can be used to prevent reblocking of PS/OSAM data sets if their names can be identified.