Disk devices

System performance is improved if storage is specified in cylinders rather than tracks or blocks. Storage on sort 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
3380	15
3390	15
9345	15

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

Allocating twice the space used by the input data sets is usually adequate for the work data sets. Certain conditions can cause additional space requirements. These include:

Long control words (more than 150 bytes)
Using different device types or work data sets
Using an alternative collating sequence
Low ratio of available storage to input file size.

Care should be taken to ensure that the LRECL parameter of the DCB corresponds to the actual maximum record length contained in your data set.