>>> Member names. The reason would be that a PDS directory is maintainedin 
order, 
> and the directory is always kept compressed.

Tom,

Thanks for the info and as mentioned earlier DFSORT has the ability of 
sorting the member names in ascending/descending order. Here is a sample 
to show just the sorting of pds member names.

//STEP0100 EXEC PGM=IKJEFT01 
//SYSTSPRT DD DSN=&&MBRS,DISP=(,PASS),SPACE=(CYL,(5,5),RLSE), 
//            DCB=(LRECL=80,RECFM=FB,BLKSIZE=0),UNIT=SYSDA 
//SYSTSIN  DD * 
  LISTDS 'USERID.PDS' MEMBERS 
//* 
//STEP0200 EXEC PGM=SORT 
//SYSOUT   DD SYSOUT=* 
//SORTIN   DD DISP=SHR,DSN=&&MBRS 
//SORTOUT  DD SYSOUT=* 
//SYSIN    DD * 
  INREC IFTHEN=(WHEN=GROUP,BEGIN=(1,11,CH,EQ,C'--MEMBERS--'), 
  END=(1,5,CH,EQ,C'READY'),PUSH=(81:ID=1)), 
  IFTHEN=(WHEN=(1,11,CH,EQ,C'--MEMBERS--',OR, 
                1,05,CH,EQ,C'READY'),OVERLAY=(81:8X)) 
 
  SORT FIELDS=(81,1,CH,A, 
               03,08,CH,D),EQUALS 
//* 

Thanks,
Kolusu
DFSORT Development
IBM Corporation

IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> wrote on 
11/20/2015 09:54:59 AM:

> From: Tom Marchant <0000000a2a8c2020-dmarc-requ...@listserv.ua.edu>
> To: IBM-MAIN@LISTSERV.UA.EDU
> Date: 11/20/2015 09:55 AM
> Subject: Re: Deleting all members of a pds
> Sent by: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU>
> 
> On Fri, 20 Nov 2015 08:11:08 -0700, Sri h Kolusu wrote:
> 
> >>>>Does it at least sort the list in descending order? 
> >
> >Descending order of what? member names or Size? Why exactly do you need 
to 
> >sort the list ? Do you think it would make a difference to the 
directory 
> >blocks?
> 
> Member names. The reason would be that a PDS directory is maintainedin 
order, 
> and the directory is always kept compressed.
> 
> Whenever a member is deleted from a PDS, the following directory 
> entries are all 
> shifted to the left. Then, if there is enough space at the end of 
> that directory 
> block, the first entry from the next block is moved to that space, 
> and the process 
> repeats to the end of the directory.
> 
> As a result, there is less I/O if they are deleted starting at the 
> end of the directory. 
> This is especially true if there are a lot of members in the PDS.
> 
> -- 
> Tom Marchant
> 
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