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Intrinsically Actuated Real Unit Operations for Virtual Unit Addressing

IP.com Disclosure Number: IPCOM000083121D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 4 page(s) / 61K

Publishing Venue

IBM

Related People

Breitenbach, RC: AUTHOR [+3]

Abstract

Common memory apparatus shared by a plurality of host CPU's, each host having an independent set of virtual address spaces, require memory-actuated operations on real disk type memory devices supporting the independent virtual addressing. Each host has independently operating chains of commands for effecting a sequence of memory operations, with respect to computer processes being executed by the host. Since the addresses of each host are independent of real unit addresses (the disk volumes VV's are also virtual, i.e., have no relationship to real memory disk packs), execution of the chains of command and other activities relating to the virtual unit addresses requires different actions by the real units.

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Intrinsically Actuated Real Unit Operations for Virtual Unit Addressing

Common memory apparatus shared by a plurality of host CPU's, each host having an independent set of virtual address spaces, require memory-actuated operations on real disk type memory devices supporting the independent virtual addressing. Each host has independently operating chains of commands for effecting a sequence of memory operations, with respect to computer processes being executed by the host. Since the addresses of each host are independent of real unit addresses (the disk volumes VV's are also virtual, i.e., have no relationship to real memory disk packs), execution of the chains of command and other activities relating to the virtual unit addresses requires different actions by the real units.

In prior systems employing real unit addressing, host generated commands relating to home address (HA) and record zero (RO) on disk files, seeks, execution of command chains, recalibrate, plus error recovery and other related functions are necessary for system support. Computer processes are not directly related to device execution; rather, all real unit activity is intrinsic to execution of memory functions in a virtual addressing mode.

The drawing shows three hosts X, Y, and Z sharing a common memory system through one or more memory adapters which, in turn, control a plurality of unit controllers A, B ... Attached to each unit controller is a set of real memory devices, for example, disk files having real addresses AA, AB, BA, BB, etc. The left character indicates the unit controller, and the right character indicates the disk file number attached to each unit controller.

The assigned address spaces for virtual address X200, mounting virtual volume 4231, having an address space of 000-255 in order of the address space are on real units AA, addresses 44-66, and AA, addresses 120-140, etc. Similarly, virtual unit Y100 mounts VV 4461 having the address space 000-255 and, in turn, is mounted on the indicated real units. Virtual unit Z40 mounts VV 3231, but only real address space BA 112-119 is allocated. That is, not all the three VV's are mounted on real space. Also, note that the lowest VV address 000 can occur on any address portion of the real units.

When the memory units are disk files and the virtual addressing is emulating to former real unit addressing, the HA (home address) and record zero (R0) become key aspects to successful operation of the shared memory with a plurality of hosts. During an HA or R0 command from any of the hosts, the first three bytes of data transferred through the memory adapter from the real memory unit contain flag and cylinder control information. The cylinder information is the real cylinder that the head actuator is presently positioned at and not the real cylinder asked for by the host.

In the event of an error, for proper sense information and ERP's (error recovery procedures), the memory adapter substitutes the present re...