RMAN : Restore SPFILE from autobackup

SPFILE is included in the controlfile autobackup. Therefore, If you loose it you can use RMAN to restore it from the autobackup.

Use below command :

RMAN> restore SPFILE from autobackup db_recovery_file_dest='/app/oracle/flash_recovery_area' db_name = 'orcl';

if you don't specify db_recovery_file_dest, by default RMAN will try to look the autobackup in $ORACLE_HOME/dbs (UNIX).

Before you can execute above command, you need to start the instance.
Use STARTUP FORCE NOMOUNT to start the instance without initialization parameter file.