Choosing an efficient block size can improve space utilization and I/O performance. DFSORT's SDB=LARGE, SDB=INPUT or SDB=YES installation option allows DFSORT to automatically select the system determined optimum block size for output data sets as long as you do not specify the BLKSIZE explicitly. Use one of these installation options, as appropriate, for optimum space utilization and performance. SDB=INPUT is the supplied default. See z/OS DFSORT Installation and Customization for details on the SDB installation option values. You can use the SDB run-time option to override the SDB installation option when appropriate for particular jobs.