Browse Prior Art Database

Handling Defective Buffer Areas

IP.com Disclosure Number: IPCOM000049976D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Christian, JH: AUTHOR [+3]

Abstract

A peripheral storage device, such as a direct-access storage device (DASD), of the disk storage apparatus type has its performance enhanced by the addition of a cache or buffer interposed between the DASD and the using host. Error conditions in the cache are handled separately for modified data M or duplicate data D. Duplicate data means the replication of the data in the cache is identical with a copy of the data in DASD. For duplicate data, a slot in error E is merely identified as being on a so-called defect list. When a cache slot or buffer area is in error-containing modified data, then that slot is on a so-called pinned list such that the data cannot be transferred to DASD.

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Handling Defective Buffer Areas

A peripheral storage device, such as a direct-access storage device (DASD), of the disk storage apparatus type has its performance enhanced by the addition of a cache or buffer interposed between the DASD and the using host. Error conditions in the cache are handled separately for modified data M or duplicate data D. Duplicate data means the replication of the data in the cache is identical with a copy of the data in DASD. For duplicate data, a slot in error E is merely identified as being on a so-called defect list. When a cache slot or buffer area is in error-containing modified data, then that slot is on a so-called pinned list such that the data cannot be transferred to DASD. If the host ever rewrites the pinned modified slot in error, then another slot is allocated and the previously pinned slot is put on the defect list.

The host operates with DASD via a cache which has addressable portions related to the addressable portions of the DASD. A directory provides addressability of all of the portions in the cache. When a slot has an error E and contains data that is a duplicate D of the DASD data, because of the duplication in DASD, the slot in error of the cache is put on a defect list such that it cannot be accessed or used via the directory. This is achieved by erasing the directory entry. A temporary data check (error) (TDC) is sent to the host to indicate that a cache error has occurred, but that the data associated with the error can be recove...