Obtaining Buffers Above 16 MB

To increase the storage area available below 16 MB for your application program, request VSAM data buffers and VSAM control blocks from virtual storage above 16 MB. To do this, specify the RMODE31 parameter on the ACB macro. See Using 31-Bit Addressing Mode with VSAM.

Optionally, specify RMODE31 in your JCL DD AMP parameter to let the user override any RMODE31 values specified when the ACB was created. If you do not specify RMODE31 in the JCL AMP parameter and the ACCBIAS value is the SYSTEM, then the default value for RMODE31 is BUFF. If the VSAM buffers are above the 16 MB line and you attempt to access them directly (as in locate mode), your program must run in 31-bit addressing mode.

If your program must run in 24-bit addressing mode and you need to access VSAM buffers directly, code RMODE31=NONE in the JCL AMP parameter.

Note: If you are opening multiple ACBS for the same data set and they are connecting to the same control block structure, the attributes defined in the first opened ACB will apply. See Sharing VSAM Data Sets.