check these links will help you
Of all the links given: I only like this:
For batch jobs, you must have the passwords in a file somewhere. One common method is to hide the password into a protected flat file with 700 permissions:
echo mysecretpassword > /tmp/mypass
chomd 700 /tmp/mypass
cat /tmp/mypass | sqlplus -s $USER << eoj >> $LOGFILE 2>&1
Is this good?