You will want to anticipate the number of tracks required for cylinder overflow areas. The computation is the same as for prime data tracks, but you must remember that overflow records are unblocked and a 10-byte link field is added. Remember also that, if you exceed the space allocated for any cylinder overflow area, an independent overflow area is required. Those records are not placed in another cylinder overflow area.

Overflow records per track = Track capacity / Length of overflow records

Example: Approximately 5000 overflow records are expected for the data set described in step 1. Because 55 overflow records will fit on a track, 91 overflow tracks are required. There are 91 overflow tracks for 155 prime data tracks, or approximately 1 overflow track for every 2 prime data tracks. Because the 3380 disk pack for a 3380 Model AD4 has 15 tracks per cylinder, it would probably be best to allocate 5 tracks per cylinder for overflow.

   Overflow  = 47968/(256+((12+267)/32)(32)+((30+267)/32)(32))
   records   = 47968/864
   per track = 55
 
   Overflow tracks required = 5000 records / 55 records per track
                            = 91
 
   Overflow tracks per cylinder = 5