Using 64-Bit Addressable Data Buffers

For each system in a sysplex, the SMSVSAM address space contains all the VSAM RLS data buffers. By default, the data buffers are contained below the 2-gigabyte virtual storage bar in a data space. To avoid possible buffer space constraints and potentially improve performance for high-transaction applications, you can optionally specify that data sets and indexes be assigned to RLS buffers with 64-bit virtual addresses, above the 2-gigabyte bar. This 64-bit virtual buffering option is provided by a combination of data class keyword and settings in the IGDSMSxx member of SYS1.PARMLIB.

To provide 64-bit data buffering for a data set with VSAM RLS, all the following must be true:

The system must be at level z/OS 1.7 or higher.
The data set or index must belong to a data class with the attribute "RLS Above the 2-GB Bar" set to Yes.
The active IGDSMSxx member of SYS1.PARMLIB must have the keyword RlsAboveTheBarMaxPoolsize set to a number between 500 megabytes or 2 terabytes for the system.

In addition, to enhance performance for each named system, whether or not the buffers are above the 2-gigabyte bar, you can set the keyword RlsFixedPoolSize in IGDSMSxx to specify the amount of total real storage to be permanently fixed to be used as data buffers.