USAGE OF SORT

The below job extracts records only if there is only one record for a key.


//************** TO ELIMINATE ALL DUPLICATES IN A FILE  ************
//STEP010  EXEC PGM=ICETOOL 
//TOOLMSG  DD SYSOUT=* 
//DFSMSG   DD SYSOUT=* 
//SYSPRINT DD DUMMY                                                  
//IN       DD DSN=XXXXXXX.TSTS.INPUT,DISP=SHR     
//OUT      DD DSN=XXXXXXX.TSTS.INPUT1,DISP=OLD    
//TOOLIN   DD *                                   
 SELECT FROM(IN) TO(OUT) ON(1,10,CH) NODUPS  
/*


The NODUPS option has to be used a little carefully, since it removes ALL the duplicate records, unlike the SUM FIELDS=NONE option in simple SORT, which retains ONE of the duplicate records.

eg) If the input is:

AAAAAAAAAA
BBBBBBBBBB
BBBBBBBBBB
BBBBBBBBBB
CCCCCCCCCC
CCCCCCCCCC
DDDDDDDDDD


The NODUPS option of ICETOOL returns:

AAAAAAAAAA
DDDDDDDDDD

whereas the SUM FIELDS=NONE option on simple SORT will return:

AAAAAAAAAA
BBBBBBBBBB
CCCCCCCCCC
DDDDDDDDDD

So, depending on your requirement, you may use either of them.
REF:http://mainframe-tips-and-tricks.blogspot.com/2011/12/sort-to-eliminate-all-duplicates.html