The announcement highlights the benefits to IMS 2.2 users of the expanded storage support embodied in the new Enterprise Systems Architecture of the E series 3090s. IMS 2.2 has been enhanced with means to use the expanded storage of ESA/370 processors and suggests that it may relieve virtual storage constraint and improve performance by reducing input-output activity. The enhancement will be available in December at no additional charge, and the company also made a statement of direction to the effect that versions of IMS will use the facilities of MVS/ESA but not yet. The enhancement to IMS 2.2 provides the facility to use the new Hiperspace data space for fast reading and writing of data using expanded storage above the 2Gb limit of MVS/XA as an extension of the current virtual storage VSAM buffer pool for full-function VSAM databases. Buffers that age out of the VSAM Buffer pool are transferred to the Hiperspace pool extension and are managed by the least recently used algorithm, in much the same way as VSAM buffer pools are managed today. IBM warns that Hiperspace pools do not apply to OSAM data bases, MSDBs, DEBDs, or VSAM subpools without buffers in multiples of 4Kb. The new facility is transparent to user applications, and can reduce the amount of VSAM read input-output activity needed for database processing. With fewer disk accesses, the average transaction elapsed time may be shortened, and the throughput capacity of IMS-dependent regions may be improved, but it all depends on things like the size of VSAM databases, the number of buffers in the Hiperspace buffer pool, read/write ratios and database record reference patterns. The use of Hiperspace, says IBM, may also provide some virtual storage constraint relief for users constrained by the DL/I private address space, since the existing size of the VSAM buffer pools could potentially be reduced if augmented with Hiperspace buffers. Benefits of using Hiperspace will be applicable to VSAM full-function DL/I data base environments, including a CICS/MVS DL/I environment, IBM says.
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