Browse Prior Art Database

Real storage management with multiple storage classifications

IP.com Disclosure Number: IPCOM000013614D
Original Publication Date: 2002-May-21
Included in the Prior Art Database: 2003-Jun-18
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Abstract

Disclosed is a method that manages real storage on systems where certain areas of real storage

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Real storage management with multiple storage classifications

Disclosed is a method that manages real storage on systems where certain areas of real storage

are more valuable (or more generally applicable) than other areas.

The z/OS* operating system is such a system where storage is classified in the following way:

(1) Below 16 Megabytes
(2) Below 2 Gigabytes, but at or above 16 Megabytes
(3) At or above 2 Gigabytes Depending on the application, virtual storage may be fixed in area (1) only, in area (1) or (2) only, or in area (1), (2) or (3). These subsections of storage are further subdivided into preferred and non-preferred, depending on whether the system has the ability to request the real storage back from the application upon demand. Fixed pages in a non-swappable address space or fixed common area storage must be backed by preferred storage because in both cases the system has no way of taking the backing real away from the application. In z/OS* and other operating systems, real storage is managed in individual units called frames (in z/Architecture* a frame is 4096 bytes). The PFTE (Page Frame Table Entry) is a data structure that represents the status of a single frame. The frames that are in use within an address space are represented by a queue of PFTEs, maintained in approximate least recently used order. The problem of managing specific classifications of storage is dealt with in z/OS* by swapping address spaces out and reclaiming their storage resources. Two problems associated with this approach are:
(1) it only deal with swappable address spaces and
(2) swapping requires I/O and is an expensive operation.

To solve this problem, a new function called the Real Storage Hierarchy Processor is given control on regular time intervals to determine whether there exists a shortage for a particular classification of storage. If there is no shortage then not...