Hi Christian,
You need to maintain it in dbenv.csh, .dbenv.sh.sapenv.csh & .sapenv.sh.
There would be similar files with .*env*<host_name>.*sh where in you will see the LD_LIBRARY_PATH Do append at the last with
<existingpath>:<you max db client path>
Do let us know if you need any further help.
Do verify after changing the environment. Logout the user and login back and do
echo $LD_LIBRARY_PATH.
regards,
Ram