The number of cylinders required to allocate prime space is determined by the number of prime data tracks required divided by the number of prime data tracks available on each cylinder. This area includes space for the prime data records, track indexes, and cylinder overflow records.

   Number of cylinders needed  = Prime data tracks needed
                                   / Prime data tracks per cylinder needed

Example: You need 155 tracks for prime data records. You can use 9.615 tracks per cylinder. Therefore, you need 17 cylinders for your prime area and cylinder overflow areas.

   Number of cylinders required = (155) / (9.615) = 16.121  (round up to 17)