A mode of operation in the version-to-version migration process during which DB2 runs the executable code for the new version, but with additional DB2 catalogue changes relative to compatibility mode. Compatibility mode* applies only to a DB2 subsystem or data sharing group that was in enabling-new-function mode (ENFM) or new-function mode (NFM) at one time. Compatibility mode* does not support fallback to a prior version of DB2. When operating in compatibility mode*, a DB2 data sharing group cannot coexist with members that operate at the prior version level. See also enabling-new-function mode, enabling-new-function mode*, compatibility mode.