Hi Jean.
1) The meaning is more or less: All changes to the database are recorded in the log (which will fill up) and you need to take care that the log is dumped (written to a file) at regular intervals or whenever it fills up over a threshold. With the dumped log files (and a backup) you can restore the database in case of a crash. So this is the setting you want to have for any productive system (as stated in the configuration Notes e.g. 1749935). The opposite setting will automaticaly truncate the log - meaning it is lost and cannot be used for a restore.
2) Yes, sp_helpdb shows only the options that are set.
2.b) The status 8705 can be seen as binary 10001000000001 (1+512+8192). The individual bits stand for different DB options: For example the 8192 means 'allow null by default'. And 'trunc log on chkpt' is 8 which is not set in this case. Details can be found in the online documentation (SyBooks Online). Both other tools (DBA Cockpit and sp_helpdb) use the system table as the data source.
By the way: in the most recent version of the DBA Cockpit there is a new screen Configuration -> SAP Configuration Check. This will use the SAP Note mentioned above and check if the settings are matching on your system. I've attached a screenshot of a system that runs with 'trunc log on chkpt' on the SID database which will show an error.
Regards,
Jan