How to recover database if system datafile lost

If system datafile removed from disk then you can  recover system datafile only in mount  state of database.

SQL> alter tablespace system offline;

alter tablespace system offline

*

ERROR at line 1:

ORA-01541: system tablespace cannot be brought offline; shut down if necessary

                                                                                                                        

 Shutdown database

SQL> shu immedaite;

SP2-0717: illegal SHUTDOWN option

SQL> shu immediate

ORA-01122: database file 1 failed verification check

ORA-01110: data file 1: '/home/oracle/10.2.0/product/oradata/orcl/system01.dbf'

ORA-01208: data file is an old version - not accessing current version

SQL> shu abort

ORACLE instance shut down.

Startup database mount stage and bring system datafile offline. And start recovery

SQL> startup mount

ORACLE instance started.

Total System Global Area  910163968 bytes

Fixed Size                  2024976 bytes

Variable Size             260049392 bytes

Database Buffers          641728512 bytes

Redo Buffers                6361088 bytes

Database mounted.

SQL>   alter database datafile 1 offline

  2  ;

Database altered.

QL>   recover datafile 1;

ORA-00279: change 1730264 generated at 04/08/2013 10:54:45 needed for thread 1

ORA-00289: suggestion :

/home/oracle/10.2.0/product/flash_recovery_area/ORCL/archivelog/2013_04_09/o1_mf

_1_46_%u_.arc

ORA-00280: change 1730264 for thread 1 is in sequence #46

Specify log: {<RET>=suggested | filename | AUTO | CANCEL}

auto

ORA-00279: change 1732717 generated at 04/08/2013 11:01:00 needed for thread 1

ORA-00289: suggestion :

/home/oracle/10.2.0/product/flash_recovery_area/ORCL/archivelog/2013_04_09/o1_mf

_1_47_%u_.arc

ORA-00280: change 1732717 for thread 1 is in sequence #47

ORA-00278: log file '/home/oracle/arch/1_46_810903019.dbf' no longer needed for

this recovery

ORA-00279: change 1733385 generated at 04/08/2013 11:01:48 needed for thread 1

ORA-00289: suggestion :

/home/oracle/10.2.0/product/flash_recovery_area/ORCL/archivelog/2013_04_09/o1_mf

_1_48_%u_.arc

ORA-00280: change 1733385 for thread 1 is in sequence #48

ORA-00278: log file '/home/oracle/arch/1_47_810903019.dbf' no longer needed for

this recovery

Log applied.

Media recovery complete.

Bring datafile open and bring database in open mode

SQL>  alter database datafile 1 online;

Database altered.

SQL>  alter database open;

Database altered.