RMAN datafiles recoevery

I am reading/testing RMAN to recover the datafiles and have questions:

basically, I am trying to resotre the datafiles or tablespaces that were lost, so obviously, the database will be crashed and you can only MOUNT the database.

Below is what Oracle advises to do and I am not clear:

Restore & Recover A Subset Of The Database
A subset of the database can be restored in a similar fashion:
run {
sql 'ALTER TABLESPACE users OFFLINE IMMEDIATE';
restore tablespace users;
recover tablespace users;
sql 'ALTER TABLESPACE users ONLINE';
}



question: you have to mount the database rights??? but I got an error:



RMAN> run {
2> sql "alter tablespace test_data offline";
3> restore tablespace test_data;
4> recover tablespace test_data;
5> sql "alter tablespace test_data online";
6> }

sql statement: alter tablespace test_data offline
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of sql command on default channel at 08/30/2005 16:47:32
RMAN-11003: failure during parse/execution of SQL statement: alter tablespace li
s_data_01 offline
ORA-01109: database not open

RMAN>


why do I get the error??? b/c the lost of the datafiels , that's only state I can get to and restore the database.

a tablespace can only be online while the database is open, so how can you take it offline?

Which part of the manuls are you having trouble with

that's exactly why I don't understand.

Ok, could you please tell me the procedure of how to restore the tablespace or datafiles using RMAN????

thanks,

tell us where you are working from and we can see what you have done / suggesting

I have catalog database running on SERVER1 and backup the database on SERVER2. SERVER2 crashed b/c it lost datafiles or its tablespaces and I have to restore the database. you can only mount the database on SERVER2 but not OPEN b/c the lost datafiles.

The thing I don't undertsand was if you lost the datafiles, the DB will crashed and it's not even online so how to take the tablespace offline and do the recovery.

I am still testing so may be I miss the puzzle somewhere, could you please tell me the whole idea to resotre the daabase if I lost the dat files.

and who on earth told you database will crash if you lose datafiles?