My database in noarchivelog mode. How I can open it?

Question

-bash-3.00$ sqlplus system as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Jul 17 15:24:45 2007
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Enter password:
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
SQL> select open_mode from v$database;
OPEN_MODE
MOUNTED
SQL> startup;
ORA-01081: cannot start already-running ORACLE - shut it down first
SQL> alter database open resetlogs;
alter database open resetlogs
ERROR at line 1:
ORA-01190: control file or data file 1 is from before the last RESETLOGS
ORA-01110: data file 1: '/oracle/app/oradata/Arju/system01.dbf'
SQL> !rman
Recovery Manager: Release 10.2.0.1.0 - Production on Tue Jul 17 15:27:28 2007
Copyright (c) 1982, 2005, Oracle. All rights reserved.
RMAN> connect target;
connected to target database: ARJU (DBID=222697548, not open)
RMAN> list backup;
using target database control file instead of recovery catalog
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
1 Full 521.71M DISK 00:01:11 11-JUL-07
BP Key: 1 Status: AVAILABLE Compressed: NO Tag: TAG20070711T105344
Piece Name: /oracle/app/flash_recovery_area/ARJU/backupset/2007_07_11/o1_mf_nnndf_TAG20070711T105344_399vqr8f_.bkp
List of Datafiles in backup set 1
File LV Type Ckp SCN Ckp Time Name
1 Full 598070 11-JUL-07 /oracle/app/oradata/Arju/system01.dbf
2 Full 598070 11-JUL-07 /oracle/app/oradata/Arju/undotbs01.dbf
3 Full 598070 11-JUL-07 /oracle/app/oradata/Arju/sysaux01.dbf
4 Full 598070 11-JUL-07 /oracle/app/oradata/Arju/users01.dbf
5 Full 598070 11-JUL-07 /oradata1/test02.dbf
BS Key Type LV Size Device Type Elapsed Time Completion Time
2 Full 6.80M DISK 00:00:01 11-JUL-07
BP Key: 2 Status: AVAILABLE Compressed: NO Tag: TAG20070711T105459
Piece Name: /oracle/app/flash_recovery_area/ARJU/autobackup/2007_07_11/o1_mf_s_627648694_399vt445_.bkp
Control File Included: Ckp SCN: 598070 Ckp time: 11-JUL-07
SPFILE Included: Modification time: 11-JUL-07
RMAN> restore database from tag TAG20070711T105344;
Starting restore at 17-JUL-07
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=158 devtype=DISK
skipping datafile 1; already restored to file /oracle/app/oradata/Arju/system01.dbf
skipping datafile 2; already restored to file /oracle/app/oradata/Arju/undotbs01.dbf
skipping datafile 3; already restored to file /oracle/app/oradata/Arju/sysaux01.dbf
skipping datafile 4; already restored to file /oracle/app/oradata/Arju/users01.dbf
skipping datafile 5; already restored to file /oradata1/test02.dbf
restore not done; all files readonly, offline, or already restored
Finished restore at 17-JUL-07
RMAN> ^D
Recovery Manager complete.
SQL> select log_mode from v$database;
LOG_MODE
NOARCHIVELOG

Answer 1

In 10gR2, you can drop a datafile, however the following restrictions apply:
* The database must be open.
* If a datafile is not empty, it cannot be dropped.
* You cannot drop the first or only datafile in a tablespace.
     (This means that DROP DATAFILE cannot be used with a bigfile tablespace.)
* You cannot drop datafiles in a read-only tablespace.
* You cannot drop datafiles in the SYSTEM tablespace.
* If a datafile in a locally managed tablespace is offline, it cannot be dropped.
Otherwise, there is no SQL command that you can issue to delete all the files associated with a tablespace and still keep the tablespace.