Using the system-managed duplexing rebuild function, you can create and maintain a duplex (secondary) copy of the lock structure in case of failure. When the structure is in duplex mode and a failure occurs, VSAM RLS switches from the failed lock structure to the active lock structure, and record-level sharing can proceed. The lock structure reverts to simplex mode, and continues to operate as it would in user-managed mode (see User-managed lock structure rebuild.)

When the lock structure is in simplex mode and DUPLEX(ENABLED) is specified for the lock structure in the CFRM active policy, the system attempts to start a system-managed duplexing rebuild if the environment allows. When DUPLEX(ALLOW) is specified, you must use SETXCF START,REBUILD,DUPLEX to manually initiate a system-managed duplexing rebuild.

You can stop system-managed duplexing manually using SETXCF STOP,REBUILD,DUPLEX or by specifying DUPLEX(DISABLED) in the CFRM active policy.

Restriction: When the lock structure is in duplex mode, user command rebuild requests are rejected. You must use the alter function to change the lock structure.

For more detailed information about the system-managed duplexing rebuild function, refer to z/OS MVS Programming: Sysplex Services Guide.