missing datafile

[sadha@exforsys]

HI,
I have a database which has been brought down since long time,when i tried to start up the database it shows that the datafile has been missing in the respective path.
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SQL> startup open pfile='/data/oracle/appsdata/tf2/IDMSREG/initIDMSREG.ora'
ORA-01081: cannot start already-running ORACLE - shut it down first
SQL> shutdown
ORA-01109: database not open


Database dismounted.
ORACLE instance shut down.
SQL> startup open pfile='/data/oracle/appsdata/tf2/IDMSREG/initIDMSREG.ora'
ORACLE instance started.

Total System Global Area 269066696 bytes
Fixed Size 451016 bytes
Variable Size 150994944 bytes
Database Buffers 117440512 bytes
Redo Buffers 180224 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 1 - see DBWR trace file
ORA-01110: data file 1:
'/data/oracle/appsdata/tf2/IDMSREG/data01/IDMSREG_system_01.dbf'

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is there any way to recover the missing datafile.
pls help its urg....