DB2_LOGGER_NON_BUFFERED_IO is OFF by default in v9.5
DB2_LOGGER_NON_BUFFERED_IO is AUTOMATIC by default in v9.7
Some links to v9.7 InfoCenter:
IBM DB2 9.7 for Linux, UNIX and Windows Information Center
IBM DB2 9.7 for Linux, UNIX and Windows Information Center
What's your experience with using buffered or non-buffered IO for transaction logs? Do you see any performance improvement / degradation?