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Browse Prior Art Database

Volume Status Change

IP.com Disclosure Number: IPCOM000112641D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Jones, I: AUTHOR [+2]

Abstract

Disclosed is a solution to the problem of Cache Invalidation where DASD units are shared by AIX* systems, using a new method termed Volume Status Change (VSC).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 58% of the total text.

Volume Status Change

      Disclosed is a solution to the problem of Cache Invalidation
where DASD units are shared by AIX* systems, using a new method
termed Volume Status Change (VSC).

      Cache invalidation is not a new problem, nor is it new to send
messages or interrupts between boxes.  Asynchronous Interrupts are
used in removable media devices and Explicit messages between lock
managers solve a similar problem.  The AIX operating system did not
provide a means for the Logical Volume Manager (LVM) to be sent
messages explicitly from other systems but they do possess a
mechanism for fielding interrupts from devices.

      If several processors can access the same data, they may take a
private copy to speed up subsequent references.  However, if one
processor needs to change the information, it must inform the others
to prevent use of out-of-date copies.  This problem is known as
'Cache Invalidation'.

      Volume Status Change provides a means to solve this problem in
the context of DASD shared by AIX systems.  (The first system which
will use VSC is HACMP/6000, which provides for application programs
to access a common database.  To prevent multiple update, locks are
used, and lock managers in each system communicate with each other.
However, this mechanism was not available to the operating system
components which provide services to the application programs, and
which cache certain control information, such as mirroring status
tables, or n...