I'm having problems getting any CLI trace info from my Perl script
(which uses DBI and DBD::DB2). I did:

db2 update cli cfg for section common using trace 1
db2 update cli cfg for section common using traceflush 1
db2 update cli cfg for section common using tracecomm 1
db2 update cli cfg for section common using \
tracefilename /tmp/test.trc

I then ran my script which does a select statement and fetches the
results, and I don't see any trace info.

Found it... the trace file was not writable by the DB2 instance user.