Read only privileges I have created a user and want to grant the user read only privileges on all database schemas. Can I do that using a single grant statement for all 20 schemas.
This may not exactly what you want, but it should be close enough.

grant read any table to username;

This provides read privileges on all user tables and views (but no privileges on dictionary tables or DBA_ catalog views).

If you want to this only for specific schemas, you need to grant the specific object privileges.