Hi,

This oracle error Action is : Enter a valid column name. A valid column name must begin with a letter, be less than or equal to 30 characters, and consist of only alphanumeric characters and the special characters $, _, and #. If it contains other characters, then it must be enclosed in double quotation marks. It may not be a reserved word.

Source : http://www.dbcodeerror .com/oracle-database-error-code-ora-00904