When a Version 3 or a Version 4 volume is mounted on an earlier MVS system, the following restrictions apply:

• Input generation data sets are not recognized because the .GxxxxVyy suffix is not part of a Version 3 or a Version 4 file identifier.
• Spanned record format is not supported.
• Data set characteristics recorded in the second header or trailer label of an input volume are not made known to the application program; instead, they must be specified either in JCL or in the DCB. (This is because the Version 3 or Version 4 MVS system code, IBMZLA, is not recognized by earlier systems.)
• A data set having a header label created by a non-MVS system with 1 or 3 in the accessibility field is treated as an MVS password-protected data set unless the volume is defined to RACF.
• A valid Version 3 or Version 4 character in the accessibility field of a header or volume label causes the volume to be rejected.
• Any output does not meet the specifications of Version 3 or Version 4 standards.