A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #
The SQL_PREFETCH_BYTES parameter appears in the [Client] section of your virtuoso.ini file.
It passes the maximum number of bytes which your server will send as prefetched rows on a forward only cursor.
If long rows are being prefetched SQL_PREFETCH_BYTES will cut off the prefetch after the number of bytes which it specifies.