International Business Machines Corporation

Paul S Frazer

John R Flanagan

Daniel Francis Casper

Kenneth J Oakes

John S Trotter

Patricia G Driever

Louis William Ricci

Catherine C Huang

Bernhard Laubli

A bi-directional and full duplex facility for permitting both the IO processor and the Channel to write CCA messages on their respective queues at the same time. IOP messages to the channel are stored on the TO_CHN queue and Channel messages to the IOP on the TO_IOP queue. CCA Queues replace hardware CCAs due to increasing transmission capabilities of current IO processors and Channel processors. Even though the mechanism is similar, the present invention provides some benefits in the use of signaling. The IOP does not have to signal the Channel each time it puts something on its outbound queue. Each queue contains multiple slots. This allows the IOP and Channel to write multiple messages on the targeted queue without encountering a CCA busy signal. The actual queues are now structured in hardware system memory.

Channel communication array queues in hardware system area

A method, program product and apparatus for checkpointing for recovery of channels in a data processing system using a protocol which allows for multiplexing operations at the frame level and streaming of commands and data. For unsuccessful retries, the correct primary CCW address is reported back to software indicating the extent to which the channel completed modifying and accessing S/390 storage.

Checkpointing for recovery of channels in a data processing system

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Poughkeepsie, NY, United States of America

Paul S Frazer