I made a full, consistent database backup with the following procedure:
shutdown immediate
startup nomount
backup database

Later I made a restore procedure of the backup with the
restore database

But after that tha restore procedure finished when I gave the
alter database open comand
I received the following error:
ORA-01113 file 1 needs media recovery
ORA-01110 data file 1 : 'D:\ORACLE\ORADATA\ZIR\SYSTEM01.DBF'
that is exactlly the system tablespace.

When I gave the
recover database
command the problem was solved, but I don't understand why do I have to start media recovery for a consistent backup.

The database is Enterprise Edition, on Windows 2000 Professional and it operates in NOARCHIVELOG.

Anny help will be appreciated.