Many thanks to everyone who has contributed to this thread. 
My tests corroborate the fact that selecting the "Display Total Tracks" option 
affects the behaviour. Also the help for the panel (in particular for that 
option) explains the behaviour I am seeing.

Ho hum. I live and learn. 46 years on mainframe and still going......

So as the OP I say,
"Great job folks, thanks for the help".

Lennie
Lennie Dymoke-Bradshaw
Consultant working on contract for BMC mainframe Services by RSM Partners
‘Dance like no one is watching. Encrypt like everyone is.’


-----Original Message-----
From: IBM Mainframe Discussion List <[email protected]> On Behalf Of 
Pommier, Rex
Sent: 15 October 2020 15:01
To: [email protected]
Subject: Re: [External] Re: ISPF dsn sort

That's not what is happening.  A different poster nailed it earlier.  If the 
"Display Total Tracks" is selected on the dataset list utility screen, the 
first time you hit PF10/11 to go right or left, ISPF needs to read the entire 
list in order to populate the "total tracks" line.  Thus you get the progress 
bar.  If you don't have that selected, ISPF only works with the screen's worth 
of data so no progress bar until you do a sort.  Once the sort is requested, 
ISPF needs to read the entire list to be able to do the sort correctly.  Once 
ISPF has all the information it needs, you can resort the data any way you want 
and it won't need to reread it.  

At least that's what I've seen with my testing of it.

Rex

-----Original Message-----
From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Bob 
Bridges
Sent: Thursday, October 15, 2020 6:02 AM
To: [email protected]
Subject: [External] Re: ISPF dsn sort

I've never noticed the behavior, but now that the OP has pointed it out, the 
reading-the-list-again explanation doesn't satisfy me.  If there's a delay and 
a progress bar when reading the list to do the sort, why is there no similar 
delay when scrolling right to see the data which (according to this 
explanation) has not yet been collected?

I'm not buying it.

---
Bob Bridges, [email protected], cell 336 382-7313

/* Our world is not divided by race, color, gender, or religion.  Our world is 
divided into wise people and fools. And fools divide themselves by race, color, 
gender, or religion.  -Mohamad Safa */

-----Original Message-----
From: IBM Mainframe Discussion List <[email protected]> On Behalf Of 
Jesse 1 Robinson
Sent: Tuesday, October 13, 2020 13:12

This is one of those IIRC posts. I think this behavior goes back decades. The 
reason is as Kolusu states. Moreover--IIRC--the very appearance of the 
'progress bar' was in response to what could be a long delay. Delay to the 
point that the user might suspect that the process was hung outright. I 
remember when the bar was introduced with that very explanation. Everything in 
those distant days was slower than today. 

As for the difference in processing, I could imagine an RFE asking for a 'quick 
sort' based only on the data previously collected and displayed. 

-----Original Message-----
From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Sri 
h Kolusu
Sent: Tuesday, October 13, 2020 9:47 AM

3.4 listing shows the list of datasets sorted on the Dataset name by default.  
Now when you issue SORT DSORG command , ISPF needs to read in the list once 
again and make DSORG as the primary key and then present you the list sorted on 
that order. You will

-----Original Message-----
From: IBM Mainframe Discussion List <[email protected]> On Behalf Of 
Lennie Dymoke-Bradshaw
Sent: Tuesday, October 13, 2020 11:18

This is something that has puzzled me for years.

I can use ISPF 3.4 to display a set of data sets. 
If I scroll right then I am shown the space usage figures.
Scroll right again and I am shown the DSORG, RECFM, Lrecl and Blksize.

If I now enter SORT DSORG I am presented with a progress bar and I am informed 
that information is being collected to perform the sort.

Given that the DSORG was already displayed, why does ISPF go and collect the 
same information again?

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