Unless SDB=NO is in effect, Blockset uses the system-determined optimum block size in most cases when the output data set block size is zero. See the discussion of the SDB option in OPTION control statement for complete details about DFSORT's use of system-determined block size.

For some jobs, the selection of a larger output data set block size can require an increase in the amount of storage needed for successful DFSORT processing.

Applications which require a specific output data set block size should be changed to specify that block size explicitly.

If SDB=NO is in effect, DFSORT selects an appropriate (though not necessarily optimum) block size for the output data set based on the available attributes from the output data set, the input data set, and the RECORD statement. The output data set block size will not necessarily be the same as the input block size.