What is a physical block? Even without taking into accounnt that contemporary
DASD subsystems are cached, on old CKD DASD you could read any of count, key
and data without reading the others.
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
עַם יִשְׂרָאֵל חַי
On 11/13/23 15:59:45, Bob Raicer wrote:
There have been a few posts in this thread that more or less stated
that only complete physical blocks could be read into storage from a
device.
This is not strictly true.>
We don't know the OP's objective: performance, security, or other.
--
gil
There have been a few posts in this thread that more or less stated
that only complete physical blocks could be read into storage from a
device.
This is not strictly true.
There is the obvious case of truncation, where the number of bytes
the device has been requested to transfer is less than
On 11/13/2023 7:23 AM, Schmitt, Michael wrote:
As long no one ever uses DISP=MOD
...or checkpoints. Checkpoints can cause short blocks to be written.
What about CLOSE TYPE=T? Would that flush the current block?
--
Phoenix Software International
Edward E. Jaffe
831 Parkview Drive North
El
At one time there was a component called Actual Block Processor that was used
both by VSAM and paging, and the paging data sets were CI format. I have no
idea how much of that, if any, remains in z/OS, but essentially my question was
whether pages were now stored in 4 KiB physical records.
A PDSE is essentially a form of VSAM Linear, where the physical data
set is a collection of 4K-byte blocks. It does not have the notion
of CA's and CI's like other VSAM data sets. The notion of BLKSIZE
is synthesized and mapped onto the internal PDSE structures; the
BLKSIZE value is not the
On 11/13/23 11:54:07, Schmitt, Michael wrote:
That I don't know. I've only dealt with GSAM checkpoints (which may not support
RECFM=VBS). And one other: checkpoints in z/OS FTP.
My *guess* is that since a checkpoint has to flush the buffers to disk before
you fill up the block, even VBS would
That I don't know. I've only dealt with GSAM checkpoints (which may not support
RECFM=VBS). And one other: checkpoints in z/OS FTP.
My *guess* is that since a checkpoint has to flush the buffers to disk before
you fill up the block, even VBS would have a short block.
-Original Message-
Same as above.
On Mon, Nov 13, 2023 at 1:50 PM Paul Gilmartin <
0014e0e4a59b-dmarc-requ...@listserv.uga.edu> wrote:
> On 11/13/23 08:23:44, Schmitt, Michael wrote:
> >>> As long no one ever uses DISP=MOD
> >
> > ...or checkpoints. Checkpoints can cause short blocks to be written.
> >
> > (My
While the original question isn't really about assembler, it is at least
about programming. This tangent has nothing to do with either... if you
want uninformed speculation on random topics, that's what IBM-MAIN is for.
sas
On Mon, Nov 13, 2023 at 9:48 AM Seymour J Metz wrote:
> I believe
On 11/13/23 08:23:44, Schmitt, Michael wrote:
As long no one ever uses DISP=MOD
...or checkpoints. Checkpoints can cause short blocks to be written.
(My knowledge is with IMS/DB GSAM checkpoints.)
How does checkpoint interact with RECFM=VBS?
--
gil
>> As long no one ever uses DISP=MOD
...or checkpoints. Checkpoints can cause short blocks to be written.
(My knowledge is with IMS/DB GSAM checkpoints.)
-Original Message-
From: IBM Mainframe Assembler List On Behalf
Of Jon Perryman
Sent: Sunday, November 12, 2023 5:18 PM
To:
I believe that the OP wanted a solution for BSAM. If VSAM is an option then
it's a nobrainer.
Does anybody know whether CI size = block size for PDSE and zFS (linear) data
sets? VSAM used to use multiple blocks for a CI.
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
עַם
Someone mentioned the CMS file system in a recent post.
The CMS file system uses a hierarchical block map system for
each file, which gives very efficient direct access by record
number (both for fixed-length and varying-length records)
avoiding the need to read any previous file data blocks
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