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.
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.