On Tue, Jul 4, 2023, 14:34 Paul Gilmartin <
[email protected]> wrote:

> On Tue, 4 Jul 2023 19:02:47 +0000, Seymour J Metz wrote:
>
> >I'm not convinced that it would have been too expensive in OS/360.
> >
> It was considered so expensive that OPEN overlays the DDNAME in
> the DCB, presumably to save 8 bytes of storage.  The DDNAME is
> unnessary after OPEN unless something goes wrong.
>
> But the original DCB is restored by CLOSE.  Where is it kept in tnhe
> meantime without using even more storage?
>

IIRC, you can chain chase from an open DCB to the TIOT entry.


> --
> gil
>
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