Patent ID: 9195394
Filing Date: 2015-11-24
Classification: G06F

Abstract:
1. A computer program product for performing an input/output (I/O) operation by a control unit configured for communication with a host computer system, the computer program product comprising: a non-transitory tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: receiving a command message at the control unit from a channel subsystem in the host computer system to initiate the I/O operation, the command message including a command for data to be transferred from the host computer system to an I/O device controlled by the control unit; and receiving a data transfer message at the control unit from the channel subsystem, the data transfer message having an amount of the data to be transferred, the amount of the data to be transferred to be less than or equal to a maximum amount of data, the maximum amount of data corresponding to a number of buffers associated with the control unit and a size of each of the number of buffers, the number of buffers indicated by a buffer credit value maintained in the host computer system, and the size indicated by a buffer size value sent from the control unit to the channel subsystem and maintained in the host computer system.