Bill,
Yes, my mistake, as you know the count has 2 digits of key length and 4 of
data length at the end.
COUNT 000D000001000000
CCCCHHHHRRKKLLLL
Or CCCCHHHHcRKKLLLL for EAS tracks
Dave
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of
Bill Fairchild
Sent: Friday, October 15, 2010 2:18 PM
To: IBM-MAIN@bama.ua.edu
Subject: Re: Null versus empty datasets
I believe you meant "the last six digits of COUNT" instead of "the 1st 4".
Bill Fairchild
Rocket Software
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of
David Kreiss
Sent: Friday, October 15, 2010 2:54 PM
To: IBM-MAIN@bama.ua.edu
Subject: Re: Null versus empty datasets
Determine what track the dataset was allocated to then run this utility
specifying the first track of the dataset.
//DFDSS EXEC PGM=ADRDSSU
//volume DD VOL=SER=volume,UNIT=3390,DISP=SHR
//SYSPRINT DD SYSOUT=*
//SYSIN DD *
PRINT TRACKS(X'00xxx',X'0000',X'00xxx',X'0000') -
INDDNAME(volume)
Here is sample:
ADR006I (001)-STEND(01), 2010.288 14:52:47 EXECUTION BEGINS
*** TRACK(CCHH) 000D0000 R0 DATA 0000000000000000
COUNT 000D000001000000
ADR006I (001)-STEND(02), 2010.288 14:52:47 EXECUTION ENDS
Note the lst 4 digits of COUNT are zero indicating a zero length block.
Dave
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of
Starr, Alan
Sent: Friday, October 15, 2010 12:41 PM
To: IBM-MAIN@bama.ua.edu
Subject: Null versus empty datasets
Hi List,
John McKown's response to Ron's S013-64 issue interested me. I had not realized
that SMS automatically wrote an EOF to newly-allocated datasets.
John pointed me to
http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/dgt2i650/8.1
which states "For sequential data sets, SMS writes a hardware EOF at the
beginning of the data set at initial allocation. This prevents data integrity
problems when applications try to read the data before data is written in the
data set."
Just for fun, I allocated four new datasets using IEFBR14:
> DSORG=PS SMS-managed
> NO DSORG SMS-managed (had to modify my DC ACS routine to get this)
> DSORG=PS non-SMS
> NO DSORG non-SMS
All utility programs (e.g. IBMGENER, IDCAMS, IEHLIST and IEBPTPCH) referencing
any of these datasets via any input DD (e.g. SYSIN or SYSUT1) recognized that
there was no data. I wonder, therefore, whether newly-allocated datasets are
now getting initialized with an "EOF". Seems unlikely to me that all are
because all JCL references up to and including V1R12 have a note for DISP=NEW
(Note: Initialize a new data set to ensure that it is empty).
I don't know of a tool that we have at this organization which indicates the
presence of an "EOF" (count with keylen=0 and datalen=0) in a track.
Would any of you have such a utility and be willing to use it to test the
results of IEFBR14-allocating the aforementioned datasets?
I'm curious to know whether newly-allocated datasets are "empty" (no content)
or "null" (hardware EOF at the beginning). I found a definition of "empty"
versus "null" in the final paragraphs of "DFSMSdfp Storage Administration:
Chapter 7. Defining data classes - Planning data classes"
Thanks,
Alan
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