Electrical computers and digital processing systems: memory – Addressing combined with specific memory configuration or... – Dynamic-type storage device
Reexamination Certificate
1998-01-05
2001-02-20
Cabeca, John W. (Department: 2752)
Electrical computers and digital processing systems: memory
Addressing combined with specific memory configuration or...
Dynamic-type storage device
C711S002000, C711S203000
Reexamination Certificate
active
06192444
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to data storage subsystems in computer systems, and more particularly to providing additional addressable functional space on a disk for use by a host processor using a virtual data storage subsystem.
BACKGROUND
Many in the field who use virtual data storage subsystems use it for the copying of logical files or volumes. Virtual refers to a functional unit that appears to be real to a host processor but where the functions are accomplished by other means. Virtual storage involves storage space that may be regarded as addressable main storage by the host processor in which virtual addresses are mapped into real addresses. The amount of virtual addresses are finite, and a host processor must first search for virtual addresses which have been flagged as available whenever it wishes to store data.
A virtual subsystem can be implemented using a Direct Access Storage Device (DASD) subsystem. The DASD subsystem allows the user to define a maximum number of a plurality (typically 256) of virtual functional devices. Each device is defined with a certain finite size, i.e., a certain number of addressable tracks. A track is a unit of space on a disk at which data can be stored. A logical file or volume is stored in a plurality of tracks. The user, either through the host processor or the DASD control panel, defines the devices on a disk to be used by the subsystem. Copies of tracks are often made to the devices for migration to permanent backup media either in parallel or at a later time. Under an existing process commonly referred to as “SnapShot”, data may only be copied either within a device or from one device to another within the subsystem. SnapShot's underlying structure is disclosed in Belsan et al., U.S. Pat. No. 5,410,667, filed Apr. 17, 1992, and is fully incorporated by reference herein. Thus, the amount of addressable space on the disk available for an execution of a copying task is limited by the size, i.e., the number of tracks, of a device. This limits the subsystem's ability to copy data.
There is a need to provide additional addressable functional space on a disk for use by the host processor using a virtual data storage subsystem. The additional addressable functional space will alleviate the host processor from having to conduct a search for available space within any device whenever space on the devices become scarce. This method and system should be cost effective, easy to implement, easily adaptable, and host processor independent. The present invention addresses this need.
SUMMARY OF THE INVENTION
A method and system in accordance with the present invention provides additional addressable space on a disk for use by a host processor with a virtual data storage subsystem. The method and system includes defining at least one of a plurality of extended image devices on a disk and requesting an instant image to be addressed to an extended image device utilizing channel command words by a host processor. The method and system also includes reading the instant image utilizing commands, such as channel command words or command descriptor blocks, by the host processor.
In a method and system in accordance with the present invention, a plurality of extended image devices are defined as extensions of primary functional device. Data may be transferred between at least one of the plurality of extended images and the primary functional device, or between at least one of the plurality of extended image devices and another of the plurality of extended image devices. An advantage of a method and system in accordance with the present invention is the availability of additional addressable space which may be used by the host processor for accomplishing the subsystem's functions, such as the copying of track pointers. By extending the amount of addressable space, the host processor is alleviated from having to conduct a search for available space within any primary functional device whenever space on the devices become scarce.
REFERENCES:
patent: 4631673 (1986-12-01), Haas et al.
patent: 4758944 (1988-07-01), Bartley et al.
patent: 5175849 (1992-12-01), Schneider
patent: 5247638 (1993-09-01), O'Brien et al.
patent: 5403639 (1995-04-01), Belsan et al.
patent: 5410667 (1995-04-01), Belsan et al.
patent: 5551003 (1996-08-01), Mattson et al.
patent: 5613113 (1997-03-01), Goldring
patent: 5778411 (1998-07-01), DeMoss et al.
patent: 5881311 (1999-03-01), Woods
Serls David
Tomsula Patrick James
White Michael Wayne
Cabeca John W.
International Business Machines - Corporation
Klein Esther E.
Sawyer Law Group LLP
Tzeng Fred F.
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