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

How List Processing Works

First define the list structure to the coupling facility. Then for each system enter a TSS MODIFY (SYSPLEX) command to define the connect‑name, structure‑names, and group‑name, and to automatically connect each system to the coupling facility.

The security file ENQ record, the first physical record in the security file, keeps control information about the security file, including file locking status. The ENQ record includes the coupling facility structure name, and the coupling facility validity record includes the volume serial number (VOLSER) of the security file. This information is stored by the first system that connects to the coupling facility structure, and is used by systems that connect subsequently to ensure that a unique security file data set and structure name combination is used among all connected systems. When a local system attempts to lock the security file, the structure name in the security file ENQ record is compared to the local system’s currently defined structure.

Whenever the security file is locked by a non‑coupling facility connected system, the structure name found within the ENQ record is validated to be active, and the local system connects to the same structure, before proceeding with any update activity against the file.

While the current system is active in the coupling facility, if the security file ENQ record is altered by another system and it no longer contains the structure name, all systems are forced to disconnect from the coupling facility.

When a coupling facility connected system manually disconnects from the structure, all other connected systems are forced to disconnect as well, to ensure that no residual data is left in the coupling facility while one of the systems is running without an XES connection. An XES sysplex connection without an XCF connection is allowed.

After a system is forced to disconnect from a structure, as a result of a manual disconnect command, all other connected systems are forced to disconnect. No re‑connect is attempted until a new structure is allocated in the coupling facility by a manual connect command, or by a new system starting up.

To determine if a structure was reallocated, use the TSS MODIFY(STATUS(SYSPLEX)) command, or the D XCF,STR z/OS operator command. Compare the current version number to the version number of the previous connection.