Multipath attached input/output control unit

A computer program product comprising:

• one or more computer-readable storage media;
• and
• program instructions stored on the one or more storage media to perform operations comprising:
• in response to experiencing a failure in one or more paths of a communication multipath attached to an input/output (I/O) control unit, receiving, from a host, a define subsystem operation (DSO) define path usage command configured to instruct the I/O control unit of expected usage of one or more specified paths in a particular path group for all devices in the path group,
• wherein the DSO define path usage command includes:
• a set first flag, the first flag being configured to restrict or allow multipath reconnections for the specified path(s) and the particular path group,
• a set second flag, the second flag being configured to restrict or allow the specified path(s) and the particular path group to present unsolicited status,
• a filled list of interface identifications (IDs) configured to determine the respective specified path(s), and
• an identified path group ID configured to determine the particular path group.

A computer system comprising:

• a processor set;
• one or more computer-readable storage media;
• and
• program instructions stored on the one or more storage media to cause the processor set to perform operations comprising:
• in response to experiencing a failure in one or more paths of a communication multipath attached to an input/output (I/O) control unit, receiving, from a host, a define subsystem operation (DSO) define path usage command configured to instruct the I/O control unit of expected usage of one or more specified paths in a particular path group for all devices in the path group,
• wherein the DSO define path usage command includes:
• a set first flag, the first flag being configured to restrict or allow multipath reconnections for the specified path(s) and the particular path group,
• a set second flag, the second flag being configured to restrict or allow the specified path(s) and the particular path group to present unsolicited status,
• a filled list of interface identifications (IDs) configured to determine the respective specified path(s), and
• an identified path group ID configured to determine the particular path group.

A method for selectively preventing use of paths of a communication multipath attached to an input/output (I/O) control unit comprising:

• experiencing a failure on one or more of the paths in the communication multipath;
• and
• in response to experiencing the failure, building and issuing a new message type with a raised attention interrupt to a host;
• receiving, from the host, a define subsystem operation (DSO) define path usage command,
• wherein the DSO define path usage command includes:
• a set first flag indicating whether multipath reconnections for the failed path(s) in a particular path group should be restricted or allowed,
• a set second flag indicating whether to restrict or allow the failed path(s) in the particular path group from presenting unsolicited statuses,
• a filled list of interface identifications (IDs) identifying the failed path(s), and
• a path group ID determining the particular path group;
• and
• using the set first flag and the set second flag to configure the failed path(s) which correspond to the filled list of interface IDs and the path group ID.

A computer system comprising:

• a processor set;
• one or more computer-readable storage media;
• and
• program instructions stored on the one or more storage media to cause the processor set to perform operations comprising:
• experiencing a failure on one or more of paths of a communication multipath attached to an input/output (I/O) control unit;
• and
• in response to experiencing the failure, building and issuing a new message type with a raised attention interrupt to a host;
• receiving, from the host, a define subsystem operation (DSO) define path usage command;
• wherein the DSO define path usage command includes:
• a set first flag indicating whether multipath reconnections for the failed path(s) in a particular path group should be restricted or allowed,
• a set second flag indicating whether to restrict or allow the failed path(s) in the particular path group from presenting unsolicited statuses,
• a filled list of interface identifications (IDs) identifying the failed path(s), and
• a path group ID determining the particular path group;
• and
• using the set first flag and the set second flag to configure the failed path(s) which correspond to the filled list of interface IDs and the path group ID.