In one aspect of buffer credit management in accordance with the present description, buffer over-commit logic determines a buffer over-commit value as, in one embodiment, proportional to a determined difference value between the average duration of an I/O operation over data transmission channels connected to a target control unit, and an average of cumulative lifespans that a set of buffers of the target control unit is committed to an I/O operation. In another aspect, buffer over-commit logic determines a buffer over-commit value as, in one embodiment, inversely proportional to buffer lifespan. In another aspect, buffer over-commit logic determines a buffer over-commit value as, in one embodiment, proportional to the determined difference value and inversely proportional to buffer lifespan. Other features and aspects may be realized, depending upon the particular application.