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A Method for Sharing *OS/390 Tape Units

IP.com Disclosure Number: IPCOM000015957D
Original Publication Date: 2002-Jun-16
Included in the Prior Art Database: 2003-Jun-21
Document File: 1 page(s) / 40K

Publishing Venue

IBM

Abstract

Disclosed is a method of automated sharing of tape units between LPARs running the *OS/390 operating system, without the need for communication between the LPARs. The method is to rely only on the tape control unit to determine the availability of a particular tape unit. When a particular LPAR requires a tape unit, the program implementing the method attempts to vary online each of the eligible tape units in turn, and uses the first one which can successfully be varied online. When the application which needed the tape unit has finished using it, the program varies it off-line so that it can be made available to other LPARs. The tape control unit is designed to ensure that its tape units can only be varied online to one LPAR at any particular time, and the invention exploits this facility. Various products exist which manage, automatically, the sharing of tape between LPARs running the OS/390 operating system, but all rely on communication between the LPARs to decide which tape unit can be used when there is a requirement for one on a particular LPAR. Communication, be it via VTAM, TCP/IP, CTC or a coupling facility, adds substantial complication and hence code size. Relying on the tape control unit for decision making simplifies the logic, thus reducing the code size, and removes the impact of any failures in the communication facilities. OS/390 is a trademark of International Business Machines Corporation in the United States, other countries, or both

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A Method for Sharing *OS/390 Tape Units

  Disclosed is a method of automated sharing of tape units between LPARs running the *OS/390 operating system, without the need for communication between the LPARs.

    The method is to rely only on the tape control unit to determine the availability of a particular tape unit. When a particular LPAR requires a tape unit, the program implementing the method attempts to vary online each of the eligible tape units in turn, and uses the first one which can successfully be varied online. When the application which needed the tape unit has finished using it, the program varies it off-line so that it can be made available to other LPARs. The tape control unit is designed to ensure that its tape units can only be varied online to one LPAR at any particular time, and the invention exploits this facility.

    Various products exist which manage, automatically, the sharing of tape between LPARs running the OS/390 operating system, but all rely on communication between the LPARs to decide which tape unit can be used when there is a requirement for one on a particular LPAR. Communication, be it via VTAM, TCP/IP, CTC or a coupling facility, adds substantial complication and hence code size. Relying on the tape control unit for decision making simplifies the logic, thus reducing the code size, and removes the impact of any failures in the communication facilities.

* OS/390 is a trademark of International Business Machines Corporation in the United...