> 
> I shall check on the use of MAX_STRING_LENGTH at least in odb itself...
> 

Ok, I looked at the use of MAX_STRING_LENGTH in ODB (odb.c):

a) it is not used in any critical places for the database itself, so it is not a limit on maximum length of TID_STRING data. good.
b) it is used in the code for saving/loading odb from .odb files (old format), not sure how it works against overlong strings, but probably 
truncates/corrupts/crashes.
c) it is used in the code for saving odb to odb.xml files. Overlong strings are truncated (I added a message about it).
d) code for loading/saving to json files handles overlong strings okey.
e) odbedit "ls" truncates overlong strings, mhttpd has some oddities against overlong strings.
f) db_sprintf() truncates string text to MAX_STRING_LENGTH to avoid output buffer overflow (should use db_snprintf() instead).

Conclusion, overlong strings should be okey, but do not use the old .odb and .xml save files. (mlogger saves odb to output .mid file in xml 
format, we should switch it to use json format).

> > CSS File = STRING : [1024] mhttpd.css
> > Sqlite dir = STRING : [1024]
> > History dir = STRING : [1024]
> > Sound = STRING : [1000] alarm.mp3
> > are exceeding the MAX_STRING_LENGTH 256 (defined in msystem.h)

So these should not cause any corruption or problem unless actual content length exceeds 255 bytes,
even then they are okey if odb is only saved and loaded into json files.

> > 1) I get the error message that some strings are too long (exceeding
> > MAX_STRING_LENGTH). Unfortunately the underlying routine doesn't tell which ODB
> > variables this is.

this is in db_check_record(), where it compares odb content with user-supplied data descriptions (there is no system-supplied
data descriptions with strings longer than MAX_STRING_LENGTH).

so I think what happened is you created a data structure with overlong strings, passed it to db_paste() or something,
db_check_record() complained about it, and db_paste() corrupted memory.

> > 
> > 2) After this reload, essentially nothing is working anymore. Any client I tried to start just crashed.
> > 

Somebody corrupted some shared memory, most likely it was db_paste() corrupted odb shared memory.

K.O.