You can code OPEN and CLOSE with MODE=31 to specify a long form parameter list that can contain 31-bit addresses. The default, MODE=24, specifies a short form parameter list with 24-bit addresses. If TYPE=J is specified, you must use the short form parameter list.

The short form parameter list must reside below 16 MB, but the calling program can be above 16 MB. The long form parameter list can reside above or below 16 MB. VSAM and VTAM® access control blocks (ACBs) can reside above 16 MB.

Although you can code MODE=31 on the OPEN or CLOSE call for a DCB, the DCB must reside below 16 MB. Therefore, the leading byte of the 4-byte DCB address must contain zeros. If the byte contains something other than zeros, an error message is issued. If an OPEN was attempted, the data set is not opened. If a CLOSE was attempted, the data set is not closed. For both types of parameter lists, the real address can be above the 2 GB bar. Therefore, you can code LOC=(xx,64) on the GETMAIN or STORAGE macro.

You need to keep the mode that is specified in the MF=L and MF=E versions of the OPEN macro consistent. The same is true for the CLOSE macro. If MODE=31 is specified in the MF=L version of the OPEN or CLOSE macro, MODE=31 must also be coded in the corresponding MF=E version of the macro. Unpredictable results occur if the mode that is specified is not consistent.