>> I'm not sure I understand what you mean; if the default volume is a
3380 and
>> the allocation is satisfied on a 3390, a larger volume, how would the
space
>> allocation be increased for the larger 3390.
Found the following info in DFSMSdfp Storage Administration Reference
(SC26-4920-01) in Chapter 3 (Creating the Base Configuration), Topic 3.2
(Defining the Base Configuration), subtopic 3.2.3 (Specifying the
Default Device Geometry):
When allocating space for a new data set on DASD, SMS converts
all space requests in tracks (TRK) or cylinders (CYL) into
requests for space in KB or MB. If a generic device type such
as the 3380 is specified, SMS uses the device geometry for
that generic device to convert tracks or cylinders into KB or
MB. If an esoteric device type such as SYSDA or no UNIT is
specified, SMS uses the default device geometry to convert
tracks and cylinders into KB or MB. If the users in your
installations specify space in tracks or cylinder units, and
they specify an esoteric UNIT or no UNIT you must specify a
default device geometry prior to converting these allocations
to system-managed data sets.
.
After SMS converts space requests to KB or MB, the space
values are passed to the ACS routines. The values are later
used to determine the number of tracks or cylinders to
allocate for the data set. The default device geometry does
not apply to objects or data sets allocated on tape.
.
There is only one Default Device Geometry for the entire SMS
complex. Default Device Geometry is an installations'
definition of how much space is represented by a TRK or a CYL
when an esoteric unit or no unit is specified.
.
The device geometry for a 3380 is 47476 bytes/track, 15
tracks/cylinder.
The device geometry for a 3390 is 56664 bytes/track, 15
tracks/cylinder.
.
It is up to each installation to decide what values to use.
>From MVS Storage Management Library: Managing Data Sets (SC26-4408):
Using Default Device Geometry:
In an SMS environment, you use default device geometry to convert
track and cylinder allocation requests to bytes. This can be used for
both SMS- and non-SMS-managed data sets. Using default device geometry
isolates users from actual physical devices; the amount of allocated
space will be consistent, regardless of which device is used.
If you specify a default device geometry, it will be used for a new
data set allocation as follows:
- When the data set is SMS-managed and a generic UNIT has not
been explicitly specified.
- When an esoteric UNIT name is specified for a non-SMS-managed
data set.
- When no UNIT name is specified for a non-SMS-managed data set,
and the default unit is esoteric. If the default unit is
generic (e.g., 3390), then the device geometry of this unit is
used for space calculations.
Ralph Kaden
z/OS (MVS) Level 2 Support - Allocation and Scheduler
(Converter/Interpreter, Initiator/Terminator, ENF, SJF, SMF, SSI, SWA Mgr)
T/ L: 8/295-4096 External: 845-435-4096
VM: S390VM.v$i01029 MVS: PLPSC.v$i316
External email: [EMAIL PROTECTED]
Internal email: Ralph Kaden/Poughkeepsie/Contr/[EMAIL PROTECTED]
William F Besnier <[EMAIL PROTECTED]>
Sent by: IBM Mainframe Discussion List <IBM-MAIN@BAMA.UA.EDU>
08/14/2008 10:07 PM
Please respond to
IBM Mainframe Discussion List <IBM-MAIN@BAMA.UA.EDU>
To
IBM-MAIN@BAMA.UA.EDU
cc
Subject
Re: DASD Space Allocation
I'm not sure I understand what you mean; if the default volume is a 3380
and
the allocation is satisfied on a 3390, a larger volume, how would the
space
allocation be increased for the larger 3390.
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On
Behalf
Of Tom Marchant
Sent: Thursday, August 14, 2008 6:05 PM
To: IBM-MAIN@BAMA.UA.EDU
Subject: Re: DASD Space Allocation
On Thu, 14 Aug 2008 17:22:35 -0400, William F Besnier wrote:
>Situation came up on a client site where they received a very large file,
>2.988 million records, and allocate the file size at (cyl,(2500,100))
with
a
>unit parameter of sysda,10; the file is received across 2 volumes in 20
>extents totaling 4,331 cylinders. I am not concerned about the extents,
what
>I don't understand is the space allocation.
If SMS is configured with a default volume specified as 3380 and the space
allocation is satisfied on a 3390, the amount allocated will be adjusted
to
account for the larger cylinders on a 3390.
--
Tom Marchant
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