Gautham,
If you want to show all of the duplicates, you can use a DFSORT/ICETOOL job like the following:
//S1 EXEC PGM=ICETOOL
//TOOLMSG DD SYSOUT=*
//DFSMSG DD SYSOUT=*
//IN DD DSN=... input file
//OUT DD DSN=... output file
//TOOLIN DD *
SELECT FROM(IN) TO(OUT) ON(1,21,CH) ALLDUPS
/*
If that doesn't give you what you want, then you need to do a better job of explaining what you do want with examples of input and expected output.
If you're not familiar with DFSORT and DFSORT's ICETOOL, I'd suggest reading through "z/OS DFSORT: Getting Started". It's an excellent tutorial, with lots of examples, that will show you how to use DFSORT, DFSORT's ICETOOL and DFSORT Symbols. You can access it online, along with all of the other DFSORT books, from:
http://www.ibm.com/support/docview.wss? ... g3T7000080