Using the Sysplex Coupling Facility › The SYSPLEX XES Function › CA Top Secret and the SYSPLEX XES Function › Direct Physical I/O Requests

Direct Physical I/O Requests

Whenever direct physical I/O is requested to the CA Top Secret database, a number of decisions must be made. It is important that any updating of any record is reflected on the database prior to the coupling facility. Most important is the need to obtain the data from the coupling facility when a direct READ of a record is requested. If any record is being updated, a lock to the coupling facility is issued to prevent the same record from being updated in the coupling facility by another CA Top Secret system. The security file ENQ record shows which system is currently holding the lock and a time stamp indicates the time the lock was placed.