Browse Prior Art Database

Scan Initiation of File Transfer Operation

IP.com Disclosure Number: IPCOM000037026D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 53K

Publishing Venue

IBM

Related People

Kiel, HG: AUTHOR [+2]

Abstract

Described is a method to optimize a file transfer operation from an independent workstation (IWS) to a host system via a workstation controller (WSC). Different scan codes (data sent from an IWS to a WSC) are used to approximate the data transfer size. WSCs no longer need to use the screen image of the IWS to transmit or receive data. Data are directly written to or read from IWS memory. This eliminates the need for the IWS to transfer the data between the screen image buffer and memory. As a result, the IWS services the file transfer request more efficiently. The performance of a system's WSC and its twinax interface overhead is one of the major contributors to a system's overall response time. This invention helps minimize the overhead to initiate file transfers.

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Scan Initiation of File Transfer Operation

Described is a method to optimize a file transfer operation from an independent workstation (IWS) to a host system via a workstation controller (WSC). Different scan codes (data sent from an IWS to a WSC) are used to approximate the data transfer size. WSCs no longer need to use the screen image of the IWS to transmit or receive data. Data are directly written to or read from IWS memory. This eliminates the need for the IWS to transfer the data between the screen image buffer and memory. As a result, the IWS services the file transfer request more efficiently. The performance of a system's WSC and its twinax interface overhead is one of the major contributors to a system's overall response time. This invention helps minimize the overhead to initiate file transfers.

Previous implementations of READ FROM IWS used a single scan code to signal the start of a file transfer. (This scan code identifies a keystroke from a terminal. The WSC recognizes this scan code as a file transfer initiation when it is received from an IWS.) This scan code implied that the WSC was to read a whole screen of information (real data or null information) and send it to the host. For file transfers less than a full screen of data, time was wasted while unnecessary data was sent to the WSC and then sent to the host system.

(Image Omitted)

This problem is solved by specifying the approximate size of the transfer. Seventeen different scan codes are used to increase the granularity of the data transfer size specification. WSCs no longer need to use the screen image of the IWS to transmit or receive data. Data are directly written to or read from IWS memory. This eliminates the need for the IWS to transfer the data between the screen image buffer and memory. As a result, the IWS can service the file transfer request more efficiently.

Each byte of data that is transferred on a twinaxial cable is contained in a unit called a frame. A frame is a total of 16 bits. Data are transmitted onto the twinaxial cable in a base band Manchester encoded format at a frequency of one bit per microsecond. Therefore, if data were being continuously transmitted one frame after another, the very best data rate that could be obtained would be 62,500 bytes of data per second.

Because of polling and command information that is required as part of this environment protocol, the maximum data rate is not obtainable. The total amount of data transferred varies depending on the number of devices attached and the polling rate. A poll sequence on the twinaxial cable per device requires 141 microseconds. For example, suppose a typical poll interval for the WSC is 16 milliseconds to each attached device and the WSC supports 40 devices. The maximum data throughput is: 62,500 Bytes - (62,500 Bytes X 141 usec X 40 X (1/16 msec)) = 40,469 bytes of data per second. Furthermore, each data transfer on this media requires sets of commands to initiate and contro...