> -----Original Message-----
> From: IBM Mainframe Discussion List [mailto:[email protected]] On
> Behalf Of Ed Gould
> Sent: Saturday, August 30, 2014 10:24 AM
> To: [email protected]
> Subject: Re: Understanding Data Set Information?
>
> On Aug 29, 2014, at 11:43 PM, retired mainframer wrote:
>
> > The ACS routines once existed in source somewhere. When they are
> > compiled into an SCDS the DSN and member names are saved in the
> > SCDS also. However, nothing prevents them from being modified
> > after compilation. (This is no different than any other source
> > library. It is a management responsibility, not the "compiler's",
> > to insure that a copy of the source corresponding to the current
> > "object" module is available for reference and future modification.)
> >
> > If your sysprog is doing his job, he can tell you where the current
> > source modules are or give you a copy. Since your dataset is not
> > SMS managed, only the DATACLAS routine has significance. Once you
> > know which data class was assigned, you will need to get the
> > attributes specified by that class (probably also from your
> > sysprog). If you have the proper authority, you can acquire this
> > information for yourself from ISMF.
>
> I answered off the top of my head and it may be incorrect.
> I understood Paul's question to be why the blocksize and the
> secondary question why did the system allocate the space it did.
> Somewhere in my past memories (and its been discussed on here a
> little) was a default geometry of 3380 NOT 3390 as you would expect.
> My memory is going here but IIRC its an easy fix but where to find it
> is another matter.
> The issue (larger) may be if it were to change would it screw up
> "other" allocations and I think IBM thinks so or they would have
> changed the default a few years ago.
> I would have expected them to do it in 2.1 as it was a major release
> but I suspect that its buried so well even IBM forgot about it.
> Ed
The question I was answering, which I included in my message but you elected
to snip, was "How do I find those?" referring to the ACS routines. It did
not ask about blocksize, allocation, or default geometry.
But as long as the issue of default geometry has come up:
System-determined block size uses the geometry of the device selected
for allocation, not the default geometry.
If the user specifies a device dependent space parameter (e.g., TRK or
CYL) while either omitting the unit or specifying the unit associated with
the default geometry, the default geometry is used to convert the space
parameter to a device independent quantity (e.g., KB or MB). If the user
does specify a different unit, the geometry of that device is used to
compute the device independent value. This value is then used to compute
the device dependent space requirement based on the default geometry. Note
that since the OP specified his space requirement in terms of bytes (which
is a device independent value), this process was not invoked for his
allocation.
Accessing the default geometry is unchanged since at least OS/390 2.10.
It is in the SCDS and can be displayed or modified using ISMF.
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