Cross-system coupling facility component of z/OS
During startup, the members of a data sharing group join one cross-system coupling facility (XCF) group, and their associated internal resource lock managers (IRLMs) join another XCF group.
The z/OS® cross-system extended services (XES) also join an XCF group implicitly on behalf of the IRLM connection to the lock structure. To join a particular group, the data sharing group members and the IRLMs use the names that you specify during Db2 installation.
Db2 uses the XCF for certain intersystem communications. Use both the coupling facility and channel-to-channel connections for XCF signaling. See Adding MVS systems to a sysplex for more information about configuring the XCF.