Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1998-11-02
2001-06-12
Breene, John (Department: 2177)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S156000, C707S793000
Reexamination Certificate
active
06247096
ABSTRACT:
DOCUMENTS INCORPORATED BY REFERENCE
Commonly assigned U.S. Pat. No. 5,546,557 is incorporated for its showing of a system for storing and managing plural logical volumes in each of several physical media volumes in an automated data storage library.
TECHNICAL FIELD
This invention relates to the management of logical volumes in a data storage subsystem, and, in particular, to the handling of eject requests from a host system for logical volumes, by a virtual media server and library manager in a data storage subsystem.
BACKGROUND OF THE INVENTION
Computer data to be stored on removable media is typically arranged in data volume units that originally corresponded to one data storage media, such as a reel of tape or tape cartridge or cassette, or an optical disk or cartridge. The capacity of such storage media has grown substantially in recent years. Thus, the average size of data sets in most computer or data processing centers is significantly less than the capacity
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of the data storage media volumes. Most programming support for peripheral data storage is directed at only the original volume units and does not provide a general solution to storing multiple data sets in the same volume. Consequently, a development for better utilizing the full capacity of a removable media cartridge (also called a media volume or a physical volume) is to store multiple volumes (called virtual or logical volumes) on a single physical volume in a stacked fashion. Data which would have been stored in multiple, mostly unused physical volumes are collected and stored on a single physical volume in separately addressable, host-processor defined logical data storage volumes. The '557 patent describes the creation and management of such logical volumes and the associated physical volumes in an automated virtual storage and retrieval library. As the result, the host processor treats only logical volumes as though they were separate physical media volumes, and the library manages the access to the logical volumes by accessing the associated physical volumes. A subsystem providing automatic management of tape data storage having such logical volumes is called a virtual media server. As can be appreciated, the management of contention for disparate logical volumes on the same physical volume can be very difficult. The patent incorporated by reference is directed to providing solutions to these problems by such a virtual media server and a library manager. The patent describes establishment of stored tables of logical volume records and of physical volume records for managing the data storage.
Presently, the typical number of logical volumes contained in a single physical volume is approximately 50. The number of cartridges stored in storage cells in a typical tape library may be 1,000, with the result that a typical virtual media server tape library, such as the IBM 3494, contains 50,000 logical volumes. Management of a virtual media server database for tracking the logical and physical volume relationship is accomplished by the virtual media server. Each of the physical volumes and its stacked logical volumes is stored in a library storage cell which is accessed by an accessor robot and delivered to a data storage drive. Operation of the library accessor is controlled by a library manager. Management of a library manager database is accomplished by the library manager for tracking the physical volumes and the storage cells.
Often, a host system will expire the data in a logical volume when it is superseded by subsequent data, or upon an administrator providing a command indicating that the data is no longer needed. It would be advantageous for the host system to “eject” the logical volume, and delete the expired logical volume from the databases, reducing the size of the databases. However, because of the fact that the logical volume is tracked by multiple databases, including databases in the host system, by the virtual media server database and by the library manager database, and there is no ability to determine whether the logical volume is clearly inactive to any host system, any attempt by a host system to eject the logical volume is currently rejected by the library manager. Thus, even though no active data is contained in the logical volume, it remains in the databases.
The only ability to eject or delete a logical volume is if the volume is newly inserted into the system and placed in an insert category, having, by definition, no active data on the logical volume.
As described in commonly assigned U.S. Pat. No. 5,546,557, host systems have programming allowing them to eject data storage volumes that are no longer needed in a data storage device, when they are operating with an individual data storage device in native mode. But there is no present method that would allow the host system to eject a logical volume from a data storage subsystem by guaranteeing that an ejected logical volume is no longer active or needed.
SUMMARY OF THE INVENTION
It is an object of the present invention to handle host system requests to eject a logical volume, without altering host system programming.
Disclosed is a method of handling eject requests of logical volumes received by a data storage subsystem from a host system. The method is implemented in a programmed data storage subsystem, an article of manufacture comprising a computer readable medium having computer readable program code embodied therein, and a computer program product. The data storage subsystem may, in a preferred embodiment, comprise a data storage library for storing and retrieving physical media volumes from storage cells, wherein the physical media volumes may contain a plurality of stacked logical volumes. The data storage subsystem has a virtual media server with a virtual media server database relating logical volumes, physical volumes and the status of the logical volumes, the status representing current operations relating to the logical volumes commanded by a host system. The data storage subsystem also has a library manager with a library manager database relating physical volumes, logical volumes, storage cells and attributes of the logical volumes.
The method comprises placing identified logical volumes in catagories as not containing active data (or scratch); receiving from the host system a request to eject a logical volume from the data storage subsystem; responding to the eject request to determine whether the requested logical volume is in a category marked as scratch; if, in the determining step, the requested logical volume is determined to be in a scratch category, notifying the virtual media server that the requested logical volume is deletable; the virtual media server, in response to the notification, determining from the virtual media server database whether the status of the requested logical volume allows deletion thereof; and if the virtual media server status determining step allows deletion of the requested logical volume, deleting the requested logical volume from both the virtual media server database and the library manager database. The method may additionally notify the requesting host system of the deletion of the requested logical volume.
For a fuller understanding of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.
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Logical Grouping of Data Storage Media in a Library System, IBM Technical Disclosure Bulletin, vol. 35, No. 5, Oct. 1992, pp. 17-20.
“IBM Magstar Model B16 Virtual Tape Server Elements of Performance” IBM Advanced Technical Support Center, Dec. 19, 1997.*
Bauske, Carl “IBM
Fisher James Arthur
Lambert Anthony Andrew
Peake Jonathan Wayne
Breene John
Holcombe John H.
International Business Machines - Corporation
Pham Khanh
Sullivan Robert M.
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