You question isn't very clear but I think what you are trying to ask is what (data dictionary) static tables and dynamic views are visible at various stages of database startup.

eg.
startup nomount
v$session - yes
dba_tablespaces - no

alter database mount;
v$session - yes
dba_tablespaces - no

alterdatabase open;
v$session - yes
dba_tablespaces - yes

Have a play on your own DB (and then hit those books to figure out why).