ORA-01157: cannot identify/lock data file 18 - see DBWR trace file
ORA-01110: data file 18: '/oracle/oradata/POL1/NETRMS_UCR.dbf'
ORA-27037: unable to obtain file status
IBM AIX RISC System/6000 Error: 2: No such file or directory
Additional information: 3
Hmm. What we got here is a link pointing to a block device. /oracle/oradata/POL1/NETRMS_UCR.dbf is a link that points to the raw device /dev/rNETRMS_UCR. Usually in a case like this, /dev/rNETRMS_UCR isn't accessible from the host. You may want to try and dd the data off that device just to verify you can access it.
Otherwise, the error is telling you Oracle can't read /oracle/oradata/POL1/NETRMS_UCR.dbf and identify it as an oracle file. I would guess it's something to do either with permissions on the device or the device has some error. I would check your system messages file (/var/adm/messages in Solaris, not sure in AIX) to see if there are any system messages with this device.