During a Pro-Designer session, you will encounter several messages generated by the program in response to an action or an operation. Possible reasons for triggering such messages are:
a) The operation was unacceptable (thus the request was not fully executed).
b) The operation lead to questionable or non-typical (but acceptable) results (the request was executed but the results should be taken with caution).
Messages of category (a) above are classified as Error Messages. The first part of their message number always starts with 1 (e.g. 109-0003). When such a message is encountered, the user should find out the cause of the error message, and take some action (adjust a parameter, save the design case file, etc.) before issuing again the same request.
Messages of category (b) above are classified as Warning Messages. The first part of their message number always starts with a 2 (e.g. 201-0005). The user does not necessarily have to take any action to prevent them from coming up. However, often times, the results of the operation requested could be doubtful. For instance, if the user sets the extent of a reaction in reaction step to 0.0, a warning will be generate. The simulation will proceed and the user can generate stream reports and economic reports. However, caution should be applied in assessing the outcome of those reports, as typically any reaction step will have a non-zero extent. Other times, warning messages will appear after a computation has been carried out but the results were deemed doubtful by the program. For instance, the Mass & Energy Balances were carried out around a unit procedure, but some (or all) of its input streams were found with zero flows.