Early termination of an I/O operation in an I/O processing system

• US 8,176,222 B2
• Filed: 02/14/2008
• Issued: 05/08/2012
• Est. Priority Date: 02/14/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Bendyk, Mark P., Carlson, Scott M., Casper, Daniel F., Flanagan, John R., Huang, Catherine C., Kalos, Matthew J., Njoku, Ughochukwu C., Ricci, Louis W., Yudenfriend, Harry M.
• Primary Examiner(s): Park, Ilwoo
• Application Number:
  US12/030,932
• Publication Number:
  US 20090210580A1
• Time in Patent Office: 1,545 Days
• Field of Search: None
• US Class Current: 710/32
• CPC Class Codes: G06F 13/122 where hardware performs an I/O function other than control of data transfer

Abstract

A computer program product, apparatus, and method for handling early termination of an I/O operation at a channel subsystem in an I/O processing system are provided. The computer program product includes a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes receiving a request to terminate an I/O operation, and transmitting an abort command to a control unit in communication with the channel subsystem in response to receiving the request to terminate the I/O operation. The method also includes transmitting a purge path command to purge a path associated with the I/O operation, where the purge path command includes an error code identifying the request to terminate the I/O operation.

Claims

1. A computer program product for handling early termination of an input/output (I/O) operation at a channel subsystem in an I/O processing system, the computer program product comprising:

a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising;

opening a first exchange and transmitting a Transport control block (TCCB) to a control unit in communication with the channel subsystem, the TCCB specifying an I/O operation to be performed;

opening a second exchange and transmitting a purge path Information Unit (IU) to the control unit, wherein the purge path IU includes an error code, the error code indicating to the control unit an error condition comprising a clear subchannel command sent from an operating system to the channel subsystem in the I/O processing system, a halt subchannel command sent from the operating system to the channel subsystem, a storage exception occurring due to an error in fetching or storing data in a host storage of a host system or a combination thereof, the host system including the channel subsystem;

receiving from the control unit a purge path response IU associated with the transmitted purge path IU; and

responsive to receiving the purge path response IU, transmitting a link level acknowledgment (LACK) to the control unit to close the second exchange.

2. The computer program product of claim 1 wherein the method further comprises transmitting a command on the first exchange to abort the first exchange in response to a request to terminate the I/O operation, wherein opening the second exchange and transmitting the purge path IU is in response to the command to abort the first exchange.

3. The computer program product of claim 2 wherein the abort command is transmitted in a first mode and the method further comprises:

switching communication protocols from the first mode to a second mode; and

transmitting a selective reset in a second mode.

4. The computer program product of claim 2, wherein the abort command is a recovery abort of the first exchange.

5. The computer program product of claim 3 wherein the first mode is a transport mode supporting a transport control word (TCW) channel program that includes the transport command control block (TCCB) configured to hold a plurality of commands, and the second mode is a command mode supporting a channel command word (CCW) channel program.

6. The computer program product of claim 1 wherein the method further comprises:

storing primary, secondary and alert status in response to transmitting the purge path command.

7. The computer program product of claim 1, wherein the purge path response IU is received using a third exchange opened and closed as part of a combined sequence.

8. The computer program product of claim 1, wherein the first exchange and the second exchange are mechanisms for transferring information between the channel and the control unit, each of the first exchange and the second exchange being opened for a respective I/O operation and used only for information transfers associated with the respective I/O operation.

9. The computer program product of claim 8, wherein the respective I/O operation associated with the first exchange is a first I/O operation identified by the TCCB, and the respective I/O operation associated with the second exchange is a purge path operation identified by the purge path IU.

10. The computer program product of claim 1, wherein the method further comprises receiving a response from the control unit in the opened first exchange.

11. The computer program product of claim 1 wherein the error code indicates the first exchange was aborted because of at least one of a clear subchannel command and a halt subchannel command.

12. The computer program product of claim 1 wherein the error code indicates the first exchange was aborted because of a storage exception.

13. An apparatus for handling early termination of an input/output (I/O) operation, the apparatus comprising:

a host computer including an operating system and a channel subsystem, the channel subsystem for communication with a control unit, the channel subsystem including one or more channels for directing information flow between memory and one or more I/O devices via the control unit, and configured to perform a method comprising;

opening a first exchange and transmitting a Transport control block (TCCB) to the control unit, the TCCB specifying an I/O operation to be performed;

opening a second exchange and transmitting a purge path Information Unit (IU) to the control unit, wherein the purge path IU includes an error code, the error code indicating to the control unit an error condition comprising a clear subchannel command sent from the operating system to the channel subsystem in the I/O processing system, a halt subchannel command sent from the operating system to the channel subsystem, a storage exception occurring due to an error in fetching or storing data in a host storage of a host system or a combination thereof, the host system including the channel subsystem;

receiving from the control unit a purge path response IU associated with the transmitted purge path IU; and

responsive to receiving the purge path response IU, transmitting a link level acknowledgment (LACK) to the control unit to close the second exchange.

14. The apparatus of claim 13, wherein the method further comprises transmitting a command on the first exchange to abort the first exchange in response to a request to terminate the I/O operation, wherein opening the second exchange and transmitting the purge path IU is in response to the command to abort the first exchange.

15. The apparatus of claim 14 wherein the abort command is transmitted in a first mode and the method performed by the channel subsystem further comprises:

switching communication protocols from the first mode to a second mode; and

transmitting a selective reset in a second mode.

16. The apparatus of claim 14, wherein the abort command is a recovery abort of the first exchange.

17. The apparatus of claim 15 wherein the first mode is a transport mode supporting a transport control word (TCW) channel program that includes a transport command control block (TCCB) configured to hold a plurality of commands, and the second mode is a command mode supporting a channel command word (CCW) channel program.

18. The apparatus of claim 13 wherein the method performed by the channel subsystem further comprises:

storing primary, secondary and alert status in response to transmitting the purge path command.

19. The apparatus of claim 13, wherein the purge path response IU is received using a third exchange opened and closed as part of a combined sequence.

20. The apparatus of claim 13, wherein the first exchange and the second exchange are mechanisms for transferring information between the channel and the control unit, each of the first exchange and the second exchange being opened for a respective I/O operation and used only for information transfers associated with the respective I/O operation.

21. The apparatus of claim 20, wherein the respective I/O operation associated with the first exchange is a first I/O operation identified by the TCCB, and the respective I/O operation associated with the second exchange is a purge path operation identified by the purge path IU.

22. The apparatus of claim 13, wherein the method further comprises receiving a response from the control unit in the opened first exchange.

23. The apparatus of claim 13 wherein the error code indicates the first exchange was aborted because of at least one of a clear subchannel command and a halt subchannel command.

24. The apparatus of claim 13 wherein the error code indicates the first exchange was aborted because of a storage exception.

25. A method for handling early termination of an input/output (I/O) operation at a channel subsystem in an I/O processing system, the method comprising:

opening a first exchange and transmitting a Transport control block (TCCB) to the control unit, the TCCB specifying an I/O operation to be performed;

opening a second exchange and transmitting a purge path Information Unit (IU) to the control unit, wherein the purge path IU includes an error code, the error code indicating to the control unit an error condition comprising a clear subchannel command sent from an operating system to the channel subsystem in the I/O processing system, a halt subchannel command sent from the operating system to the channel subsystem, a storage exception occurring due to an error in fetching or storing data in a host storage of a host system or a combination thereof, the host system including the channel subsystem;

receiving from the control unit a purge path response IU associated with the transmitted purge path IU; and

responsive to receiving the purge path response IU, transmitting a link level acknowledgment (LACK) to the control unit to close the second exchange.

26. The method of claim 25, further comprising transmitting a command on the first exchange to abort the first exchange in response to a request to terminate the I/O operation, wherein opening the second exchange and transmitting the purge path IU is in response to the command to abort the first exchange.

27. The method of claim 26 wherein the abort command is transmitted in a first mode and the method further comprises:

switching communication protocols from the first mode to a second mode; and

transmitting a selective reset in a second mode.

28. The method of claim 26, wherein the abort command is a recovery abort of the first exchange.

29. The method of claim 27 wherein the first mode is a transport mode supporting a transport control word (TCW) channel program that includes a transport command control block (TCCB) configured to hold a plurality of commands, and the second mode is a command mode supporting a channel command word (CCW) channel program.

30. The method of claim 25 further comprising:

storing primary, secondary and alert status in response to transmitting the purge path command.

31. The method of claim 25, wherein the purge path response IU is received using a third exchange opened and closed as part of a combined sequence.

32. The method of claim 25, wherein the first exchange and the second exchange are mechanisms for transferring information between the channel and the control unit, each of the first exchange and the second exchange being opened for a respective I/O operation and used only for information transfers associated with the respective I/O operation.

33. The method of claim 32, wherein the respective I/O operation associated with the first exchange is a first I/O operation identified by the TCCB, and the respective I/O operation associated with the second exchange is a purge path operation identified by the purge path IU.

34. The method of claim 25, further comprising receiving a response from the control unit in the opened first exchange.

35. The method of claim 25 wherein the error code indicates the first exchange was aborted because of at least one of a clear subchannel command and a halt subchannel command.

36. The method of claim 25 wherein the error code indicates the first exchange was aborted because of a storage exception.