Db2 for z/OS support for asynchronous CF duplexing

When the coupling facility (CF) is set up in duplex mode, Db2 for z/OS data sharing performance can improve if asynchronous CF duplexing is in effect.

With asynchronous CF duplexing, multi-site data sharing groups that implement duplexing all Db2 CF structures can have continuous availability without significant performance impact after site failures.

Asynchronous CF duplexing for the lock structure has the following prerequisites:

• Firmware support for Coupling Facility Control Code (CFCC) with service level 02.16
• CF-to-CF connectivity through coupling links

If those prerequisites are met, you can enable asynchronous CF duplexing by setting the DUPLEX option in the coupling facility resource management (CFRM) policy to one of the following values:

• DUPLEX(ENABLED,ASYNCONLY)
• DUPLEX(ENABLED,ASYNC)
• DUPLEX(ALLOWED,ASYNCONLY)
• DUPLEX(ALLOWED,ASYNC)

For more information, see CFRM options for duplexing in Db2 data sharing.

Switching from asynchronous CF duplexing

You can switch from asynchronous CF duplexing to a simplex lock structure or to synchronous duplexing of the lock structure at any time by changing the CFRM policy for the lock structure, and rebuilding the lock structure to activate the new policy.