Configures the Berkeley DB logging subsystem.
The syntax of this parameter in the DB_CONFIG file is
a single line with the string log_set_config,
one or more whitespace characters, method flag parameter as a string,
optionally one or more whitespace characters, and the string on or off.
If the optional string is omitted, the default is on.
The method flag parameters are:
Turns off system buffering of Berkeley DB log files to avoid double caching.
Configures Berkeley DB to flush log writes to the backing disk before returning from the write system call, rather than flushing log writes explicitly in a separate system call, as necessary.
For more information, see DbEnv::log_set_config().