Oracle Database Discussions

Hello,

I am running a Oracle 8.1.7.0.0 database and cannot connect to it. When I try using sqlplus and entering in sys as sysdba and then entering the password I get a ORA-01033 error. I can connect to the database using sqlplus /nolog, but when i try to open the database I get this error:
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SQL> alter database open
2 /
alter database open
*
ERROR at line 1:
ORA-01110: data file 12: '/var/oracle/u01/app/oracle/oradata/wxdb/system10.dbf'
ORA-01115: IO error reading block from file 12 (block # 1)
ORA-27069: skgfdisp: attempt to do I/O beyond the range of the file
Additional information: 1
Additional information: 1
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So then I tried to take the DBF file offline with and got this error
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SQL> alter database datafile '/var/oracle/u01/app/oracle/oradata/wxdb/system10.dbf' offline;
alter database datafile '/var/oracle/u01/app/oracle/oradata/wxdb/system10.dbf' offline
*
ERROR at line 1:
ORA-01145: offline immediate disallowed unless media recovery enabled
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Now, I am at a loss since I do not know how to enable media recovery.

-Joseph