During the merge job the worm tapes are rejected with IOCHNBLK3 and ARCCTYPE not NULL
IEC705I TAPE ON xxxx,0TBDCW,SL,COMP,jobname,DMS.S01,data set name6,MEDIA2,LOGICAL WORM
hh.mm.ss JOBnnnnn IOS000I xxxx,99,FPR,01,0600,,**,0TBDHR,P00RZDMS 629
629 80460030002A27202224(B31000011E001F00)0000(510001FF)CE1F340CFEC50B00
629 WORM OVERWRITE REJECTED
Release : Disk Backup and Restore 12.5
To correct this problem the PTF LU06393 should be applied.