Extended Processing Cabinett, XPC. På Bilregistret användes den som I/O-cache. Minskade åtkomsttiden till diskarna
”OS 2200 systems may be clustered to achieve greater performance and availability than a single system. Up to 4 systems may be combined into a cluster sharing databases and files via shared disks. A hardware device, the XPC-L, provides coordination among the systems by providing a high-speed lock manager for database and file access.
A clustered environment allows each system to have its own local files, databases, and application groups along with shared files and one or more shared application groups. Local files and databases are accessed only by a single system. Shared files and databases must be on disks that are simultaneously accessible from all systems in the cluster.
The XPC-L provides a communication path among the systems for coordination of actions. It also provides a very fast lock engine. Connection to the XPC-L is via a special I/O processor that operates with extremely low latencies. The lock manager in the XPC-L provides all the functions required for both file and database locks. This includes deadlock detection and the ability to free up locks of failed applications.
The XPC-L is implemented with two physical servers to create a fully redundant configuration. Maintenance, including loading new versions of the XPC-L firmware, may be performed on one of the servers while the other continues to run. Failures, including physical damage to one server, do not stop the cluster, as all information is kept in both servers.”