We can calculate the number of CIs within a CA that will be left free at
load time if we know the number of CIs in the CA and the CA Freespace percentage.
NumFree = Ceil(CISinCA * CAFRSPC%)
Where:
NumFree == Number of CIs not initially loaded
Ceil == function that returns the integer value rounded up
CISinCA == Number of CIs in the CA
CAFRSPC% == Defined CA free space percentage
To determine the number of CIs in a CA, you first need
to know the CA Size.
The CA Size is the smallest of:
- The primary space allocation amount
- The secondary space allocation amount
- The size of one cylinder
If allocations are specified in cylinders, or (in VSE's implementation)
if the amount of track or record allocations (both primary and secondary amounts) are
at least the size of one cylinder, then the CA size will be one cylinder.
You need to know the physical characteristics of the disk device
being used (or simulated, in the case of virtual disks or Multiprise Internal Disk
subsystems). For example, a 3390 device contains 15 tracks per cylinder, with
room on each track for:
- 2 26KB CIs
- 6 8KB CIs
- 12 4KB CIs
and so on. For details about the number of CIs that can be contained
on one cylinder (the maximum CA size), you can refer to the VSE/VSAM User's Guide
manual... or look at this link (not yet working...)
