Level 23 coupling facility

A level 23 coupling facility (CFLEVEL=23) provides the following enhancements:

• Asynchronous Cache Cross-Invalidation (XI)
  • Asynchronous Cache Cross-Invalidation (XI) is a sysplex capability for performance, scalability, and improved cross-site operation. This function allows the cache coherency messages that flow around the sysplex to maintain data integrity to be performed in an asynchronous fashion rather than synchronously. Exploitation must provide support to sync up with the asynchronous cross-invalidate messages at critical points in its processing, such as at transaction commit. The asynchronous protocol is expected to reduce CF cache structure service times and sysplex coupling overhead, particularly in sysplex environments that involve multiple sites with significant cross-site distances involved. The asynchronous protocol avoids some of the distance latencies associated with the communication of XI messages across inter-site distance.