IBM 890 manual z/Architecture Operating System Support

z/Architecture

The zSeries is based on the z/Architecture™, which is designed to reduce bottlenecks associated with the lack of addressable memory and automatically directs resources to priority work through Intelligent Resource Director (IRD). The z/Architecture is a 64-bit superset of ESA/390.

z/Architecture is implemented on the z890 to allow full 64- bit real and virtual storage support. A maximum 32 GB of real storage is available on z890 servers. z890 can defi ne any LPAR as having 31-bit or 64-bit addressability.

z/Architecture has:

•64-bit general registers.

•New 64-bit integer instructions. Most ESA/390 architec- ture instructions with 32-bit operands have new 64-bit and 32- to 64-bit analogs.

•64-bit addressing is supported for both operands and instructions for both real addressing and virtual addressing.

•64-bit address generation. z/Architecture provides 64-bit virtual addressing in an address space, and 64-bit real addressing.

•64-bit control registers. z/Architecture control registers can specify regions, segments, or can force virtual addresses to be treated as real addresses.

•The prefi x area is expanded from 4K to 8K bytes.

•New instructions provide quad-word storage consis- tency.

•The 64-bit I/O architecture allows CCW indirect data addressing to designate data addresses above 2 GB for both format-0 and format-1 CCWs.

•IEEE Floating Point architecture adds twelve new instructions for 64-bit integer conversion.

•The 64-bit SIE architecture allows a z/Architecture server to support both ESA/390 (31-bit) and z/Architecture (64- bit) guests. Zone Relocation is expanded to 64-bit for LPAR and z/VM®.

•64-bit operands and general registers are used for all Cryptographic instructions

•The implementation of 64-bit z/Architecture can help reduce problems associated with lack of addressable memory by making the addressing capability virtually unlimited (16 Exabytes).

z/Architecture Operating System Support

The z/Architecture is a tri-modal architecture capable of executing in 24-bit, 31-bit, or 64-bit addressing modes. Operating systems and middleware products have been modifi ed to exploit the new capabilities of the z/Architecture. Immediate benefi t can be realized by the elimination of the overhead of Central Storage to Expanded Storage page movement and the relief provided for those constrained by the 2 GB real storage limit of ESA/390. Application programs can run unmodifi ed on the zSeries family of servers.

Expanded Storage (ES) is still supported for operating sys- tems running in ESA/390 mode (31-bit). For z/Architecture mode (64-bit), ES is supported by z/VM. ES is not supported by z/OS in z/Architecture mode.

Although z/OS and z/OS.e do not support Expanded Stor- age when running under the new architecture, all of the Hiperspace™ and VIO APIs, as well as the Move Page (MVPG) instruction, continue to operate in a compatible manner. There is no need to change products that use Hiperspaces.

Some of the exploiters of z/Architecture for z/OS include:

•DB2 Universal Database™ Server for z/OS

•IMS™

•Virtual Storage Access Method (VSAM)

•Remote Dual Copy (XRC)

•Tape and DASD access method

5