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Why we will create the load module in PDS only
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Mamata Patel

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PostPosted: Sat Apr 10, 2010 11:32 am    Post subject: Why we will create the load module in PDS only
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Please help me to get the exact reason of below question.

why we will create the load module in PDS only, why not in PS data set?

Thanks in Advance.
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enrico-sorichetti

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PostPosted: Sat Apr 10, 2010 11:46 am    Post subject: Reply to: Doubt in JCL........
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because the whole thing was designed this way!

99% of the times the why is ...
see the first line icon_biggrin.gif
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dick scherrer

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PostPosted: Sat Apr 10, 2010 11:49 am    Post subject:
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Hello and welcome to the forum,

Because modules are executed from "load libraries" which contain additonal information about the modules.

Also, simple arithmetic. . . Better to keep track of 1 pds with 5,000 modules than 5,000 files . . .
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Mamata Patel

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PostPosted: Sat Apr 10, 2010 2:36 pm    Post subject:
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Thanks for ur reply. if have only one module eventhough we will use PDS only why?. I want specific reason.
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Marso

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PostPosted: Sat Apr 10, 2010 3:06 pm    Post subject:
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Mamata Patel wrote:
I want specific reason.

You've got 2 very good reasons already. Why do you want more?
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enrico-sorichetti

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PostPosted: Sat Apr 10, 2010 3:17 pm    Post subject: Reply to: Why we will create the load module in PDS only
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Quote:
I want specific reason.

again only the system designers can tell You the reason icon_evil.gif

when You design something from scratch what are the reasons for one choice rather than another one?

an external mind can only guess!

for load modules the reason to use PDS is hidden in a much higher design document

same applies to why some BINDER object ( load modules ) MUST be stored in a PDSE
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PeterHolland

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PostPosted: Sat Apr 10, 2010 3:45 pm    Post subject:
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Long long ago programs were run by reading in a (with a card reader)
deck of binary punch cards. After that one could put those decks (for different programs on tape and by means of label processing choose
a program to run (GE-400 series i worked with). Then the same could be done by putting the programs on disk. Since VSAM was not invented yet
(if yes maybe that was chosen) the PDS was invented.

Previous story i told my kids to get to sleep.
And hey it was working.
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enrico-sorichetti

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PostPosted: Sat Apr 10, 2010 5:14 pm    Post subject: Reply to: Why we will create the load module in PDS only
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Quote:
(GE-400 series i worked with)


the GECOS was a great operating system
too bad that I threw away quite a few manuals
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PeterHolland

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PostPosted: Sat Apr 10, 2010 5:23 pm    Post subject:
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Quote:

the GECOS was a great operating system
too bad that I threw away quite a few manuals


Same here. It was great fun working with the GE-437.
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enrico-sorichetti

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PostPosted: Sat Apr 10, 2010 5:49 pm    Post subject: Reply to: Why we will create the load module in PDS only
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not even the interviewer knows !
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PeterHolland

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PostPosted: Sat Apr 10, 2010 6:22 pm    Post subject: Re: Reply to: Why we will create the load module in PDS only
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enrico-sorichetti wrote:
not even the interviewer knows !



Just old hands like you and me.
I even worked with the gamma-30. Programmed in French.
Branchez a droit/gauche instructions.
Pupitre = console.

That was really nice.
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CICS Guy

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PostPosted: Sat Apr 10, 2010 6:51 pm    Post subject:
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enrico-sorichetti wrote:
because the whole thing was designed this way!

dick scherrer wrote:
Because modules are executed from "load libraries".
Also, simple arithmetic. . . Better to keep track of 1 pds with 5,000 modules than 5,000 files . . .
Please don't forget that DOS was here before OS and, in some small way, PDSs do seem to resemble core, relo and source libs....grin....
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enrico-sorichetti

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PostPosted: Sat Apr 10, 2010 10:08 pm    Post subject: Reply to: Why we will create the load module in PDS only
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I worked at something even better...
the ELEA 6001 from OLIVETTI Italy

DECIMAL repeat DECIMAL machine with memory sizes in increment of 10000 <things>
with a COBOL compiler in ITALIAN

smart machine... everything was variable length...
the <byte> was made of the 4 (IIRC) data bits,parity bit, stop bit
the storage address in the machine instruction was reversed
so that the high order digits were taken from the previous instruction
there was no need to specify the operands lengths because it was determined by the stop bit

the registers were simply a storage location addressed as registers
to <save> the registers You did not have to save them, it was enough to point the register area to a different storage address
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PeterHolland

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PostPosted: Sat Apr 10, 2010 10:48 pm    Post subject:
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Jees Enrico,

you are that old? icon_smile.gif
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enrico-sorichetti

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PostPosted: Sat Apr 10, 2010 10:56 pm    Post subject: Reply to: Why we will create the load module in PDS only
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Quote:
you are that old?

what do You mean that old icon_question.gif icon_evil.gif icon_wink.gif

if You want to play around with cryptography
http://ibmmainframes.com/viewtopic.php?t=47119&postdays=0&postorder=asc&start=30
should be quick enough to find out even by brute force!
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dick scherrer

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PostPosted: Sun Apr 11, 2010 1:05 am    Post subject: Reply to: Why we will create the load module in PDS only
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Quote:
DECIMAL repeat DECIMAL machine with memory sizes in increment of 10000 <things> with a COBOL compiler in ITALIAN
Our decimal machine (Burroughs 200/300 series) had only 4.8k of fixed-length "things" - we'd have sold our soul for 10k - let alone multiples of 10k. . .

No COBOL - only assembler. Neither tape nor disk - cards in, cards or paper out.

And this was the 3rd "stored program" computer i worked on (before that wired panels). . .

Quote:
Please don't forget that DOS was here before OS and, in some small way, PDSs do seem to resemble core, relo and source libs....grin....
Once upon a time it was told that OS was supposed to be "up and running" before there was a DOS and that DOS was put together and released to keep this computing environment (s360 and subsequent) moving forward. Back then were many hardware choices and IBM surely did not want to be left out due to Operating System problems as the move from tabulating machines to "real computers" unfolded.

d
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MBabu

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PostPosted: Sun Apr 11, 2010 5:18 am    Post subject:
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Neither of the two answers (it is what it is because it is, and because it is, so there) are answers to the question. The reason is that you can't use a PS directly is that there is metadata associated with executables that is stored in the PDS or PDSE directory. The load process uses the directory to determine things like amode, rmode, execute vs no-execute, etc. A PS does not have a place to store that metadata. Why would it be designed that way? Probably because reading a PDS directory is very fast as opposed to opening a sequential data set for each load module just to determine its attributes. Also, the system can cache TTRs (physical locations from which to read the module) quickly. I don't know why it was designed the way it was, but the reason you can't use a PS is the data in the directory. Its the same reason that you can't copy a load module (w/o the directory) to a PS and expect it to ever work again. As mentioned, you can store unlinked object in a PS and the loader can handle that but that is not a load module.
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enrico-sorichetti

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PostPosted: Sun Apr 11, 2010 12:23 pm    Post subject: Reply to: Why we will create the load module in PDS only
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Quote:
Neither of the two answers (it is what it is because it is, and because it is, so there) are answers to the question. The reason is that you can't use a PS directly is that there is metadata associated with executables that is stored in the PDS or PDSE directory.


Quote:
I don't know why it was designed the way it


so You do not know the answer either icon_biggrin.gif

why the metadata is stored in the pds directory ?
why...
why...
repeat with me ... because of the design,
so the only people who know the real reason are those who designed the whole thing

You are giving as a why the details of the implementation ( meatadata <stuff> )
but that' s not a reason just the visible part of the design
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MBabu

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PostPosted: Mon Apr 12, 2010 1:23 am    Post subject:
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with all due respect, that is silly. no one asks a question so that they can be told 'because it is that way'. Questions are asked because people want useful information. The question implies a search for the reason behind the design. The 'thats the way it is designed' answer is just like asking a doctor "why am I sick" and getting the response "because you aren't healthy". Its useless, pointless, and insulting, and appears to be intended to be degrading.

I have to say that the whole tenor of this board is one of people answering questions with pointless, insulting responses. Just like the history of the other mainframe boards, it appears to be experienced people who want to keep their hand in the mainframe game, but are upset that jobs are moving to India or elsewhere so they treat the new people, those asking questions, as the enemy, and as idiots.

No - I don't know the reason for the original design. But I do know the consequences of doing what the question asks about. If speculating on the reason for the design is bad then call me wicked. But at least I'm not going to insult the intelligence of the original poster.
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Ronald Burr

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PostPosted: Mon Apr 12, 2010 2:08 am    Post subject:
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@MBabu -
Apart from a full explanation from the original designers, I think that your explanation is most reasonable.
It should be apparent to any programmer worthy of the title that opening/reading/processing ( a set of ) PDS/PDSE directories is leaps and bounds faster than opening/reading/processing each and every physical sequential file that the directory entries represent in order to derive the needed information ( e.g. how much storage to GETMAIN in order to bring a load module into core, where to load it ( above/below the line), etc. ). Directories also facilitate the use of concatenated libraries and the use of member aliases. Think of what it would be like to do that with PS files - without degrading both performance and maintenance ( Imagine what hoops would have to be jumped thru for LNKLIST or a CICS PCT without the use of PDS/PDSE's ). Ewww. Wouldn't want to go there.
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