Checkpointing for recovery of channels in a data processing system
AssigneeInternational Business Machines Corporation
InventorsPatricia G. Driever, John R. Flanagan, Paul S. Frazer, Catherine C. Huang, Bernhard Laubli, Louis W. Ricci
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Abstract
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.
Claims36
A method of checkpointing for recovery of a channel connected to a control unit in a data processing system using a protocol which allows for multiplexing operations at the frame level, said method comprising:
- tracking within the channel, the progress of multiple Channel Command Words (CCWs) through their various stages;
- detecting when an error occurs and an operation is aborted;
- selecting which CCW to attempt to retry based on the progress of the multiple CCWs;
- and
- said tracking within the channel includes keeping track of;
- the last-completed CCW number,
- the last-received CCW number,
- the last-expected CCW number, and
- the last-assigned CCW number.
A computer program product comprising a computer useable medium having computer readable program code means therein for checkpointing for recovery of a channel connected to a control unit in a data processing system using a protocol which allows for multiplexing operations at the frame level, said computer readable program code means in said computer program product comprising:
- computer readable program code means for tracking within the channel, the progress of multiple Channel Command Words (CCWs) through their various stages;
- computer readable program code means for detecting when an error occurs and an operation is aborted;
- computer readable program code means for selecting which CCW to attempt to retry based on the progress of the multiple CCWs;
- and
- said computer readable program code means for tracking includes computer readable program code means for keeping track of;
- the last-completed CCW number,
- the last-received CCW number,
- the last-expected CCW number, and
- the last-assigned CCW number.
An apparatus for checkpointing for recovery of a channel connected to a control unit in a data processing system using a protocol which allows for multiplexing operations at the frame level, said apparatus comprising:
- means for tracking within the channel, the progress of multiple Channel Command Words (CCWs) through their various stages;
- means for detecting when an error occurs and an operation is aborted;
- means for selecting which CCW to attempt to retry based on the progress of the multiple CCWs;
- and
- said means for tracking includes means for keeping track of;
- the last-completed CCW number,
- the last-received CCW number,
- the last-expected CCW number, and
- the last-assigned CCW number.
An apparatus comprising:
- a data processing system;
- a channel in said data processing system
- a control unit connected to said channel using a protocol which allows for multiplexing operations at the frame level;
- computer readable program code for tracking within the channel, the progress of multiple Channel Command Words (CCWs) through their various stages;
- computer readable program code for detecting when an error occurs and an operation is aborted;
- computer readable program code for selecting which CCW to attempt to retry based on the progress of the multiple CCWs;
- and
- said computer readable program code for tracking comprises computer readable program code for keeping track of;
- the last-completed CCW number,
- the last-received CCW number,
- the last-expected CCW number, and
- the last-assigned CCW number.
Dependencies are inferred from the claim text.