This is too long for a comment so I'll add an answer. XHDR seems to be the header structure of the log file. I found this info here
As for LFL I have not found anything which makes me wonder whether this is some kind of abbreviation similar to LOTCH (LOCK/LATCH)?
(Since the question was resurrected, I guess I'll add my 2 cents.)
I would verify, if the username conforms to the DB2 naming rules. Since you used authentication plugin previously, I suspect you could ignore those naming rules. Now that you created the user on the server directly, you need to follow them. Here's the link to the rules:
a simple answer - user db2smth need the 'connect' privilege --
you can try :
db2 connect to dbname user db2inst1
GRANT CONNECT ON DATABASE TO USER db2smth
How do I grant all privileges to local db2admin with DB2 9.7 on Windows?