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Browse Prior Art Database

Handling Device Service Requests In A Cached Device Environment

IP.com Disclosure Number: IPCOM000048875D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Christian, JH: AUTHOR [+5]

Abstract

In a cached environment for peripheral systems such as storage systems employing direct-access storage devices (DASDs), the handling of device service requests on a realtime basis presents unique problems. Management of the cache by the processor controlling the peripheral system requires extensive attention. During this management, if a plurality of devices are awaiting arrival of a given data area to a transducer, the frequency of polling for DASD service requests becomes critical. To alleviate this situation, the buffer control program examines the device interface on a short poll basis for detecting certain device service requests relating to accessing the devices.

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Handling Device Service Requests In A Cached Device Environment

In a cached environment for peripheral systems such as storage systems employing direct-access storage devices (DASDs), the handling of device service requests on a realtime basis presents unique problems. Management of the cache by the processor controlling the peripheral system requires extensive attention. During this management, if a plurality of devices are awaiting arrival of a given data area to a transducer, the frequency of polling for DASD service requests becomes critical. To alleviate this situation, the buffer control program examines the device interface on a short poll basis for detecting certain device service requests relating to accessing the devices. When such a request is detected during cache or data buffer management, a low entry to a direct control queue avoids polling host attachment requests and enables handling time- dependent requests in an efficient manner. An alternative is to limit the work of the data management in the cache area. This approach does tend to limit the effectiveness of cache management. The interleaving of polling of the devices with subsequent clean-up of cache management followed by a request to the direct control enhances the total system operation.

The figure shows access to DASD from a plurality of hosts through a host attachment and a direct control with a device interface. Access to a data buffer is through a buffer control and the host attachment. Further, the the buffer control can access the direct control for implementing data transfers between DASD and the data buffer. The host attachment, direct control, and buffer control are a combination of electronic circuits and a programmed processor. The direct control is that ele...