Oracle:er det muligt at oprette et synonym til et skema?

Ja, du kan oprette synonymer til et skema.

select ksppinm, ksppstvl from x$ksppi a, x$ksppsv b where a.indx=b.indx and ksppinm like '%schema%synonym%'
ALTER SYSTEM SET  "_enable_schema_synonyms" = true SCOPE=SPFILE;
STARTUP FORCE
show parameter synonym

Forudsat at du allerede har et skema ved navn ORA...

CREATE SCHEMA SYNONYM  ORASYN for ORA;   -- create synonym for schema
CREATE TABLE ORASYN.TAB1(id number(10)); -- create table in schema

Mere information her:http://oracle- network.com/database/how-to-create-synonym-for-a-schema/