olemus
andmebaasi skeemi objekt, viit pöördumiseks teise andmebaasi objektide poole
= a schema object in one database that enables to access objects on another database
https://docs.oracle.com/cd/E24693_01/server.11203/e17120/img/admin045.png

näiteid
https://docs.oracle.com/cd/E18283_01/server.112/e17120/ds_concepts002.htm
https://www.enterprisedb.com/edb-docs/d/edb-postgres-advanced-server/user-guides/database-compatibility-for-oracle-developers-guide/9.5/Database_Compatibility_for_Oracle_Developers_Guide.1.065.html