Thanks for the answer. “su” is working fine, I could switch from root to user, from user to user etc. with su – <username>. Here’s the default /etc/pam.d/su config used on the SLES10SP2 server:
#%PAM-1.0
auth sufficient pam_rootok.so
auth include common-auth
account include common-account
password include common-password
session include common-session
session optional pam_xauth.so