Error:cannot backup SPFILE because the instance was not started with SPFILE

Question

I get the following error message, what I have done wrong?
Starting backup at 27-JUN-08
released channel: ch1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of backup command at 06/27/2008 10:11:54
RMAN-06062: can not backup SPFILE because the instance was not started with SPFILE
Best Regards,
Fan

Answer 1

Show parameter pfile/spfile will not show you contents of pfile , for seeing contents you will have to show parameter with required parama name.
show parameter log_archive_dest
Whenever you start database ostartup first by default use spfile$Oracle_Sid.ora for starting the instance if this spfile does not exist then it goes for spfile.ora if spfile.ora also does not exist then it search init$Oracle_Sid.ora in default location.
As you created spfile after restarting the database will automatically use spfile and will show you spfile in yours param when you will show parameter spfile if it does not show then you are still using pfile
SQL> startup pfile='C:\oracle\product\10.1.0\admin\lease\pfile\init.ora.5242008172537'
ORACLE instance started.
Total System Global Area  171966464 bytes
Fixed Size                   787988 bytes
Variable Size             145488364 bytes
Database Buffers           25165824 bytes
Redo Buffers                 524288 bytes
Database mounted.
Database opened.
SQL> show parameter pfile
NAME                                 TYPE        VALUE
spfile                               string
SQL> create spfile from pfile
  2  /
File created.
SQL> show parameter pfile
NAME                                 TYPE        VALUE
spfile                               string
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area  171966464 bytes
Fixed Size                   787988 bytes
Variable Size             145488364 bytes
Database Buffers           25165824 bytes
Redo Buffers                 524288 bytes
Database mounted.
Database opened.
SQL> show parameter pfile
NAME                                 TYPE        VALUE
spfile                               string      C:\ORACLE\PRODUCT\10.1.0\DB_2\
                                                 DATABASE\SPFILELEASE.ORA
SQL>