Restore / Recover / Overall nice treatment of UNDO

Question

Hi,
I'm updating our 'Backup and Recovery Bible' which was written when UNDO was but a twinkle in the eye of Oracle Developers. I'm a bit unsure of how recovery should be done in the event that the UNDO tablespace or any of its datafiles dies.
I do know that I can create another UNDO tablespace if for example we lose one of the datafiles that isn't being used at the time of the failure. But could someone point me to a good link or comment on what should be done if we have a problem with UNDO in terms of restore / recover / RMAN usage etc.
We're using both 9i and 10g on Solaris. For the moment no interface to a media manager.
Cheers.

Answer 1

Confusion sets in.
I don't understand why (after renaming an undo datafile to OFF_undo) I'm not getting anything in the v$recover_file view.
undo datafile name changed
SQL> create table lambda (col1 varchar2(10)) tablespace users;
create table lambda (col1 varchar2(10)) tablespace users
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-01116: error in opening database file 2
ORA-01110: data file 2: '/database/data01/z111ot11/undo_01.dbf'
ORA-27041: unable to open file
SVR4 Error: 2: No such file or directory
Additional information: 3
SQL> SELECT FILE#, ERROR, ONLINE_STATUS, CHANGE#, TIME
FROM V$RECOVER_FILE; 2
no rows selected
SQL> COL DF# FORMAT 999
SQL> COL DF_NAME FORMAT A35
SQL> COL TBSP_NAME FORMAT A7
SQL> COL STATUS FORMAT A7
SQL> COL ERROR FORMAT A10
SQL> COL CHANGE# FORMAT 99999999
SQL> SELECT r.FILE# AS df#, d.NAME AS df_name, t.NAME AS tbsp_name,
2 d.STATUS, r.ERROR, r.CHANGE#, r.TIME
3 FROM V$RECOVER_FILE r, V$DATAFILE d, V$TABLESPACE t
4 WHERE t.TS# = d.TS#
5 AND d.FILE# = r.FILE#
6 ;
no rows selected
Nothing in the alert.log either. If the UNDO is that important - why isn't the database screaming at me?