create user proxy1 identified by proxy1;
alter user main_user grant connect through proxy1;
connect proxy1[main_user]/proxy1@SID;
Now we are connected, let's check current user:
show user;
Output:
user is main_user
====== Change only the default schema ======
alter session set current_schema=other_schema_name
Check if the schema was changed:
select sys_context( 'userenv', 'current_schema' ) from dual;