According to https://help.univention.com/t/p/22821 a warning should appear in 5.2 when using tdb. This seems not to be the case atm. root@dn1:~# univention-app info UCS: 5.2-0 errata0 Installed: letsencrypt=4.0.0-1 samba4=4.21 univention-demo-data=2.1.0-1 5.0/keycloak=25.0.6-ucs4 Upgradable: root@dn1:~# ucr search samba/database/backend/store samba/database/backend/store/size: 8Gb Specifies the maximum size of the database, currently only supported by the mdb backend (default 8Gb). samba/database/backend/store: mdb Specifies the database backend to be used (default is mdb, alternative option is tdb). Changing this requires a re-join of univention-samba4. root@dn1:~# univention-run-diagnostic-checks -t 42_samba_tdb_deprecated Executing following checks: ['42_samba_tdb_deprecated'] You can find the logging messages of the diagnostic modules at /var/log/univention/management-console-module-diagnostic.log ran 42_samba_tdb_deprecated successfully. root@dn1:~# ldbsearch -H /var/lib/samba/private/sam.ldb -b '@PARTITION' -s base backendStore | sed -n 's/^backendStore: //p' tdb