Specifying the storage of checkpoints on DASD

When you have calculated the number of 4K records for the checkpoint, use Table 1 to determine the number of tracks or cylinders on DASD, and round up to the nearest whole number.

Table 1. Number of 4K records per track and cylinder for various DASD devices
DASD Device Type	3380	3390	9340
# of 4K Records per Track	10	12	10
# of 4K Records per Cylinder	150	180	150

Note:

Track 1 contains only the Check, Lock, and Master records, plus as many change log records (4K each) that will fit on the remainder of the track. Track 1 correction is needed because track 1 is typically not filled to capacity.
The change log records can overflow onto subsequent tracks.
If the data set is not large enough, JES2 issues the $HASP296 message to indicate the number of additional tracks required. (There is no penalty for over-estimating the number.)

For example, 4K records require the following amount of space on DASD Device Type 3380 or 3390, if the number of 4K records for type 3380 is 376 and the number of 4K records for type 3390 is 378:

DASD Device Type 3380:: 38 tracks (376 / 10 = 37.6), or 3 cylinders (376 / 150 = 2.5)
DASD Device Type 3390:: 32 tracks (378 / 12 = 31.5), or 3 cylinders (378 / 180 = 2.1).