Thanks dandycomp, this seems to work in VIYA SPRE.
I never used an authentication domain before.
After creating new Domain and set the correct Authorisation group on this domain, as being member of this authorisation group I can access the LIBNAME as :
libname test db2 authdomain="SCHULDERAuth" Datasrc=SCHULDER SCHEMA=DWSCHULDEN;
When not being member of the authorisation group on this domain, no access is allowed.
in code :
NOTE: Credential could not be obtained from Viya credentials service.
WARNING: No login information was available for authdomain SCHULDERAuth.