The CMP PARM determines how PD and ZD control fields will be compared. When CMP=CPD is in effect, the Compare Decimal (CP) instruction may be used under certain circumstances for the compare. ZD fields are packed and then compared. This method has performance advantages. However, invalid PD data may cause a system 0C7 abend and program termination. Moreover, the integrity of ZD fields is only guaranteed when they contain valid ZD data. The CMP=CPD method will not be used for control fields that exceed 16 bytes or for variable-length merges when an even value (0, 2, 4, or 6) is specified for the VLTEST PARM.
When CMP=CLC is in effect, no data validation is performed and the integrity of the output is maintained, even if the sign for a PD or ZD field is invalid. This method will be used if any control field exceeds 16 bytes or for variable-length merges when an even value is specified for the VLTEST PARM.