In JCL FILE RECFM and LRECL being changed by the system with BLKSIZE=0

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Issue/Introduction

submitting jcl with the following....
//OUTFILE  DD DSN=HLQ.XXXX.XXXXX,DISP=(,CATLG),
//            UNIT=3390,SPACE=(CYL,(5,5),RLSE),
//            DCB=(RECFM=FB,LRECL=255,BLKSIZE=0)

But file being created is as RECFM=VB and LRECL=255

another example is  
//OUTFILE  DD DSN=HLQ.XXXX.XXXXX,DISP=(,CATLG),
//            UNIT=3390,SPACE=(CYL,(5,5),RLSE),
//            DCB=(RECFM=FB,LRECL=80,BLKSIZE=0)

file being created is also RECFM=VB and LRECL=255

Resolution

The customer's environment was automatically changing any file defined with BLKSIZE=0 to RECFM=VB and LRECL=255.
The workaround was to use a BLKSIZE that wasnt 0 for eg...
DCB=(RECFM=FB,LRECL=80,BLKSIZE=8000)