Method for avoiding interface errors during controller recovery
Original Publication Date: 2002-Sep-01
Included in the Prior Art Database: 2003-Jun-21
When a storage controller in a network performs internal recovery, there are cases where I/O (Input/Output) operations from hosts are purged. Disclosed is an algorithm that is designed to reduce or eliminate unnecessary error recovery and error reports by systems in a network when a storage controller device in that network is performing internal recovery. In current implementations, operations which are active on the I/O interface are terminated using link level facilities such as connection recovery on *ESCON interfaces and ABTS (Abort Sequence) on **FICON interfaces. These interface recoveries cause messages to operators when logged by the host system, and cause further levels of recovery at said host system. Disconnected operations are then terminated by sending unit check status with appropriate sense after the internal recovery is complete. A preferred algorithm avoids these interface errors by gracefully terminating the connected operations with unit check status prior to performing the interface recovery. The problems which must be solved to do this are: 1) Internal Recovery must be performed quickly. Handshaking with the host to terminate the operations may take too long.