Disk capacity considerations

You can specify a mixture of disk devices for a given sort application. Any IBM disk device supported by your operating system can be used for work data sets.

For best performance, use high-speed devices such as IBM's TotalStorage DS8000 storage subsystems for work data sets.

System performance is improved if work data sets are specified in cylinders, rather than tracks or blocks. Storage on temporary work data sets will be readjusted to cylinders if possible. The number of tracks per cylinder for disk devices is shown in Table 1.

Table 1. Number of Tracks per Cylinder for Disk Devices
Number of Tracks per Cylinder for Disk DevicesDevice	Tracks per Cylinder	Maximum Bytes used per Track
3380	15	47476
3390	15	56664
9345	15	46456

If WRKSEC is in effect and the work data set is not allocated to VIO, DFSORT allocates secondary extents as required, even if not requested in the JCL.