This statement tries to apply BUFFERED LOG mode, but the database is ANSI compliant; that is, it was created with the clause MODE ANSI. One aspect of ANSI compliance is that all transactions are logged immediately during the execution of the COMMIT WORK statement. The use of a buffered log entails a deferred write of log records. It improves performance at some slight risk of failing to log a transaction. Such a risk is not allowed under the standard; an ANSI-compliant database must use unbuffered logging.