How does oracle accesses v$ tables or views in mount state

Hi All,
I want to know how oracle accesses fixed tables/views while the database is in mount state.
I did the following:
1. Started the database in mount state.
2. Query v$database ,v$datafile--Successful
3. Queried dba_data_files.---ERROR
SQL> select * from dba_data_files;
select * from dba_data_files
ERROR at line 1:
ORA-01219: database not open: queries allowed on fixed tables/views only
As per my understanding goes,all these tables are a part of Data Dictionary which is stored physically on system tablespace.
Now since the database is mounted ,it cannot access any part of system tablespace's data.Am I right??
So how does it queries v$ tables and other fixed database tables in mount state???
Thanks in advance
Saket Bansal

the v$(dynamic) view comes from instance
the dba(static) views comes from dictionary
but there is only one view can be look while instance is in nomount mode
and that is
v$instance ,,,
BUT ONLY THING I DON KNOW IS WHY WE CAN STILL DESCRIBE THE V$ VIEWS WHILE INSTANCE IS IN NOMOUNT MODE,,,
ORACLE instance shut down.
SQL> startup nomount;
ORACLE instance started.
Total System Global Area 285212672 bytes
Fixed Size 1248576 bytes
Variable Size 75498176 bytes
Database Buffers 205520896 bytes
Redo Buffers 2945024 bytes
SQL> desc v$datafile;
Name Null? Type
FILE# NUMBER
CREATION_CHANGE# NUMBER
CREATION_TIME DATE
TS# NUMBER
RFILE# NUMBER
STATUS VARCHAR2(7)
ENABLED VARCHAR2(10)
CHECKPOINT_CHANGE# NUMBER
CHECKPOINT_TIME DATE
UNRECOVERABLE_CHANGE# NUMBER
UNRECOVERABLE_TIME DATE
LAST_CHANGE# NUMBER
LAST_TIME DATE
OFFLINE_CHANGE# NUMBER
ONLINE_CHANGE# NUMBER
ONLINE_TIME DATE
BYTES NUMBER
BLOCKS NUMBER
CREATE_BYTES NUMBER
BLOCK_SIZE NUMBER
NAME VARCHAR2(513)
PLUGGED_IN NUMBER
BLOCK1_OFFSET NUMBER
AUX_NAME VARCHAR2(513)
FIRST_NONLOGGED_SCN NUMBER
FIRST_NONLOGGED_TIME DATE
SQL> desc v$tablespace;
Name Null? Type
TS# NUMBER
NAME VARCHAR2(30)
INCLUDED_IN_DATABASE_BACKUP VARCHAR2(3)
BIGFILE VARCHAR2(3)
FLASHBACK_ON VARCHAR2(3)
ENCRYPT_IN_BACKUP VARCHAR2(3)
HOW DOES THIS COME FROM ????
Edited by: jignesh kankrecha on Jul 6, 2009 8:12 AM

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