I keep on seeing from AI 56,664 bytes per tack for 3390 pack how is that
determined


Joe Reichman

On Mon, Jun 29, 2026 at 8:58 PM Attila Fogarasi <
[email protected]> wrote:

> The net bytes (i.e. longest record you can write to that track) varies by
> access method as there is overhead (control bytes).  TRKCALC is provided to
> compute the largest record which can fit on a track (using EXCP), see
>
> https://www.ibm.com/docs/en/zos/3.2.0?topic=instructions-performing-track-calculations-trkcalc-macro
>
> Unless you are using EXCP the hardware track capacity is irrelevant, the
> access method used will determine the actual bytes per track (and varies by
> BLKSIZE).
>
> On Tue, Jun 30, 2026 at 10:35 AM Joseph Reichman <
> [email protected]> wrote:
>
> > Would anyone know how to get the net bytes per track for a 3390
> >
> > I have been using devtype ddname,buffer,devtab
> >
> >
> > Where buffer is a 32 byte output field
> >
> > But it keeps on coming back with the overhead of 58,864
> >
> > I think the net is 56,664
> >
> > I would like to get that figure programmatically instead of hard coding
> it
> >
> > Thanks
> >
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