Semi-Synchronous Cached DASD
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2005-Feb-19
An adaptive synchronous/buffered operation for direct-access storage devices (DASDs) enhance storage subsystem operations by molding caching operations with direct access to DASD for optimizing subsystem throughout, and the control is particularly useful for count, key, data (CKD) formatted data storage. CKD operation in DASD requires highly responsive I/O channels and control units. Response time is critical for reconnection after a disconnected SET SECTOR CCW and between CCWs (channel command words) after track synchronization has been achieved. As channel utilization increases, the probability of reconnection during the SET SECTOR window decreases. Missing this window causes an additional disk rotation to bring the window back under the read/write head.