i found one way


MAN> allocate channel for delete type disk;

MAN-03022: compiling command: allocate
MAN-03023: executing command: allocate
MAN-08030: allocated channel: delete
MAN-08500: channel delete: sid=10 devtype=DISK

MAN> change backuppiece 'c:\0_602178238' delete;

MAN-03022: compiling command: change
MAN-03023: executing command: change
MAN-08073: deleted backup piece
MAN-08517: backup piece handle=C:\0_602178238 recid=5 stamp=602178242
MAN-03023: executing command: partial resync
MAN-08003: starting partial resync of recovery catalog
MAN-08005: partial resync complete

MAN> report obsolete;

MAN-03022: compiling command: report
MAN-06280: Report of obsolete backup sets and datafile copies
MAN-06281: Type Recid Stamp Filename
MAN-06282: -------------------- ------ --------- --------------------------
MAN-06284: Backup Set 11 602527592
MAN-06285: Backup Piece 11 602527580 C:\BKPL0602527575
MAN-06284: Backup Set 8 602339721
MAN-06285: Backup Piece 8 602339711 C:\TESTBACKUP602339707


if u know a way where one need not give backuppiece name explicitly,plz let me know
thanks for ur support