Environment:
OS: IBM AIX 5.1
DB: Oracle9i R9.2


I am getting this error when selecting from the tables in this tablespace:

ORA-01157: cannot identify/lock data file 18 - see DBWR trace file
ORA-01110: data file 18: '/oracle/oradata/POL1/NETRMS_UCR.dbf'

I checked the file does exist in the specified location.

Thanks for all the replies.