Behavior of Oracle Database in case Media Failure on datafile

Key Word: Oracle, Media Failure, SYSTEM Tablespace
  If the instance cannot write to a datafile in the SYSTEM tablespace, an undo tablespace (if the database is in automatic undo management mode, which is the preferred choice in Release 10g), or a datafile in a tablespace containing active rollback segments (if in manual undo management mode), then the database issues an error and shuts down the instance. All files in the SYSTEM tablespace and all datafiles containing rollback segments must be online in order for the database to operate properly.
  If an instance cannot write to a datafile other than those in the preceding list, then the result depends on whether the database is running in ARCHIVELOG mode or not.
  In ARCHIVELOG mode, the database records an error in the database writer trace file and takes the affected datafile offline. (All other datafiles in the tablespace containing this datafile remain online.) You can then rectify the underlying problem and restore and recover the affected tablespace.
  In NOARCHIVELOG mode, the database writer background process DBWR fails, and the instance fails, the cause of the problem determines the required response. If the problem is temporary (for example, a disk controller was powered off), then crash recovery usually can be performed using the online redo log files. In such situations, the instance can be restarted without resorting to media recovery. However, if a datafile is damaged, then you must restore a consistent backup of the entire database.