Allocating Paths to Queued I/O Requests
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-09
This invention relates to a method for allocating path availability to queued I/O requests accessing a common device to which a state variable (activity number) counterpart to each path is incremented when a Start I/O (SIO) issues over that path and is decremented when a channel program is completed. The method contemplates that if at least two paths are free, then the path having the lowest number is assigned. Further, in the event that only one path is free, this path is assigned only if its new activity number following the assignment will not exceed a threshold that depends on both the activity number on another channel and on a parameter THRESH.