# US 2018/0024902 A1 · Detection and recovery of lost host enabled facilities > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0024902 A1 - Document ID: US20180024902A1 - Status: Published application - Kind: A1 - Application number: 15/214,584 - Filed: 2016-07-20 - Published: 2018-01-25 - Earliest claimed: 2016-07-20 - Assignees: International Business Machines Corporation - Applicants: International Business Machines Corporation - Inventors: Scott B. Compton; Dale F. Riedy; William C. Shepard - Web page: https://patentgrep.com/patent/US20180024902A1 ## CPC - G06F 11/004: {Error avoidance (G06F11/07 and subgroups take precedence)} - G06F 11/3048: {where the topology of the computing system or computing system component explicitly influences the monitoring activity, e.g. serial, hierarchical systems} - G06F 11/00: Error detection; Error correction; Monitoring (error detection, correction or monitoring in information storage based on relative movement between record carrier and transducer G11B20/18; monitoring, i.e. supervising the progress of recording or reproducing G11B27/36; in static stores G11C29/00) - G06F 11/3034: {where the computing system component is a storage system, e.g. DASD based or network based (digital input from or digital output to record carriers G06F3/06; digital recording or reproducing G11B20/18; for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS], H04L67/1097)} - G06F 11/3055: {Monitoring arrangements for monitoring the status of the computing system or of the computing system component, e.g. monitoring if the computing system is on, off, available, not available (error or fault processing without redundancy G06F11/0703; error detection or correction by redundancy in data representation G06F11/08; error detection or correction of the data by redundancy in operations G06F11/14; error detection or correction by redundancy in hardware G06F11/16)} - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract A method, system, and computer program product are provided for determining whether a control unit for an attached device has lost knowledge of a supported host enabled facility associated with the attached device. I/O instructions are initiated that include a first instruction to determine whether the control unit currently has knowledge of the host enabled facility and a second instruction providing knowledge of the host enabled facility by the control unit. Based on responses from the control unit to the I/O instructions, it is determined whether the control unit has transitioned from not having knowledge of the host enabled facility to having such access. If it is determined that the control unit has made such transition as a result of the sequence of I/O instructions, parameters for use with the host enabled facility are initialized; otherwise, such initialization is prevented. ## Claims ### Claim 1 A computer-implemented method for determining whether a control unit for an attached device has lost knowledge of a host enabled facility associated with the attached device, the method comprising: initiating a sequence of I/O instructions to the control unit that includes a first instruction to determine whether the control unit currently has knowledge of the host enabled facility and a second instruction providing knowledge of the host enabled facility to the control unit; based at least in part on one or more responses from the control unit to the sequence of I/O instructions, determining whether the control unit has transitioned from a first state in which the control unit does not have knowledge of the host enabled facility to a second state in which the control unit has knowledge of the host enabled facility; and based at least in part on a determination that the control unit has transitioned from the first state to the second state as a result of the sequence of I/O instructions, initializing one or more parameters for use with the host enabled facility, and otherwise preventing the initializing of the one or more parameters. ### Claim 2 (depends on 1) The computer-implemented method of claim 1 wherein the attached device is a storage device, wherein the host enabled facility is a parallel access volume support facility, and wherein the one or more parameters include one or more aliases for use in accessing the attached device. ### Claim 3 (depends on 1) The computer-implemented method of claim 1 wherein the method is performed in response to an instruction to mount the attached device for use by the control unit. ### Claim 4 (depends on 1) The computer-implemented method of claim 1 wherein the sequence of I/O instructions includes two or more identical instructions to read one or more characteristics of the attached device. ### Claim 5 (depends on 1) The computer-implemented method of claim 1, further comprising determining whether the attached device is to be brought online and, responsive to such determining, delaying initializing of the one or more parameters until the attached device is to be brought online. ### Claim 6 (depends on 1) The computer-implemented method of claim 1, wherein determining whether the control unit has transitioned from the first state to the second state includes determining that the control unit is likely to have transitioned, and wherein initializing the one or more parameters for use with the host enabled facility is performed in response to such determining. ### Claim 7 (depends on 1) The computer-implemented method of claim 1 wherein initializing the one or more parameters for use with the attached device includes setting one or more flags to prevent an additional performance of the method during the initializing. ### Claim 8 A non-transitory computer-readable medium having stored contents that, when executed, configure a computing system to perform a method for determining whether a control unit for an attached device has lost knowledge of a host enabled facility associated with the attached device, the method comprising: initiating a sequence of I/O instructions to the control unit that includes a first instruction to determine whether the control unit currently has knowledge of the host enabled facility and a second instruction providing knowledge of the host enabled facility by the control unit; based at least in part on one or more responses from the control unit to the sequence of I/O instructions, determining whether the control unit has transitioned from a first state in which the control unit does not have knowledge of the host enabled facility to a second state in which the control unit has knowledge of the host enabled facility; and based at least in part on a determination that the control unit has transitioned from the first state to the second state as a result of the sequence of I/O instructions, initializing one or more parameters for use with the host enabled facility, and otherwise preventing the initializing of the one or more parameters. ### Claim 9 (depends on 8) The non-transitory computer-readable medium of claim 8 wherein the attached device is a storage device, wherein the host enabled facility is a parallel access volume support facility, and wherein the one or more parameters include one or more aliases for use in accessing the attached device. ### Claim 10 (depends on 8) The non-transitory computer-readable medium of claim 8 wherein the stored contents further configure the computing system to perform the method in response to an instruction to mount the attached device for use by the control unit. ### Claim 11 (depends on 8) The non-transitory computer-readable medium of claim 8 wherein the sequence of I/O instructions includes two or more identical instructions to read one or more characteristics of the attached device. ### Claim 12 (depends on 8) The non-transitory computer-readable medium of claim 8, wherein the stored contents further configure the computing system to determine whether the attached device is to be brought online and, responsive to such determining, to delay initialization of the one or more parameters until the attached device is to be brought online. ### Claim 13 (depends on 8) The non-transitory computer-readable medium of claim 8, wherein determining whether the control unit has transitioned from the first state to the second state includes determining that the control unit is likely to have transitioned, and wherein the stored contents further configure the computing system to initialize the one or more parameters for use with the host enabled facility is performed in response to such determining. ### Claim 14 (depends on 8) The non-transitory computer-readable medium of claim 8 wherein initializing the one or more parameters for use with the attached device includes setting one or more flags to prevent an additional performance of the method during the initializing. ### Claim 15 A system for determining whether a control unit for an attached device has lost knowledge of a host enabled facility associated with the attached device, comprising: one or more processors; and at least one memory, the memory including instructions that, upon execution by at least one of the one or more processors, cause the system to perform a method, the method including: initiating a sequence of I/O instructions to the control unit that includes a first instruction to determine whether the control unit currently has knowledge of the host enabled facility and a second instruction providing knowledge of the host enabled facility by the control unit; based at least in part on one or more responses from the control unit to the sequence of I/O instructions, determining whether the control unit has transitioned from a first state in which the control unit does not have knowledge of the host enabled facility to a second state in which the control unit has knowledge of the host enabled facility; and based at least in part on a determination that the control unit has transitioned from the first state to the second state as a result of the sequence of I/O instructions, initializing one or more parameters for use with the host enabled facility, and otherwise preventing the initializing of the one or more parameters. ### Claim 16 (depends on 15) The system of claim 15 wherein the attached device is a storage device, wherein the host enabled facility is a parallel access volume support facility, and wherein the one or more parameters includes one or more aliases for use in accessing the attached device. ### Claim 17 (depends on 15) The system of claim 15 wherein the instructions cause the system to perform the method in response to an instruction to mount the attached device for use by the control unit. ### Claim 18 (depends on 15) The system of claim 15 wherein the sequence of I/O instructions includes two or more identical instructions to read one or more characteristics of the attached device. ### Claim 19 (depends on 15) The system of claim 15, wherein the method further comprises determining whether the attached device is to be brought online and, responsive to such determining, delaying initializing of the one or more parameters until the attached device is to be brought online. ### Claim 20 (depends on 15) The system of claim 15, wherein determining whether the control unit has transitioned from the first state to the second state includes determining that the control unit is likely to have transitioned, and wherein the instructions cause the system to initialize the one or more parameters for use with the host enabled facility in response to such determining.