Technique for Unexpected Data Attention Handling
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
This technique improves performance of the AS400 Storage Subsystem by eliminating queueing delays resulting from unexpected data attentions. In DFCI-based storage systems, it is advantageous for the controller to transfer the command packet to the DFCI slave before setting up the data transfer because this permits the time spent initializing the controller hardware to be overlapped with the DASD seek time, which is typically several milliseconds. However, occasionally the disk is already at the desired disk cylinder position and the slave raises its Attention signal for data transfer before the DASD I/O processor has finished its setup.