1. Create a message in Oracle Apps

Resp: Application Developer
Nav: Application > Messages

(For example XXAP999_SUPPLIER_ERR, containing the token &VENDOR_NUM)

2. For a token-substituted message use the following PL/SQL to do the substitution:

BEGIN
  fnd_message.set_name('XXAP', 'XXAP999_SUPPLIER_ERR');
  fnd_message.set_token('VENDOR_NUM', '12345678');
END;

Then use fnd_message.get to retrieve the message string. E.g.

SELECT fnd_message.get
FROM   dual

For non-substituted messages, the set_name and set_token commands are not required. Just use:

SELECT fnd_message.get_string('XXAP', 'XXAP999_SUPPLIER_ERR')
FROM   dual

3. To print to standard concurrent program output or log files do the following:
Set a text string variable, for example

v_msg := fnd_message.get

Then print it to the log or output files:

fnd_file.put_line(fnd_file.log, 'Error message is: ' || v_msg);
fnd_file.put_line(fnd_file.output, 'Error message is: ' || v_msg);