Q: Postgres: GRANT usage on schema myschema to myrole; Error I'm new to Postgres (worked with Oracle the last 23 years).
I would like to grant the usage on schema to role. But that seems to be impossible:
ps >create role marco_role;
CREATE ROLE
ps >create schema myschema;
CREATE SCHEMA
ps >grant usage on myschema to marco_role;
FEHLER:  Relation »myschema« existiert nicht (English: Relation does not exists)

What is my problem? 

A: To grant privileges on a schema you need to use ON SCHEMA as documented in the manual
grant usage ON SCHEMA myschema to marco_role;
You probably also want to define default privileges for new tables (that are not yet created) as well: 
alter default privileges  
   in schema myschema
   grant select on tables to marco_role;

