Debugging and dealing with error messages
IBM ILOG CPLEX Optimization Studio checks for and displays syntax errors and solving errors.
Syntax errors
Syntax and semantic errors are displayed dynamically in the Problems tab as you type.
For example, a common error is to forget to put a semicolon at the end of a statement. If you omit the semicolon at the end of the line
int P = ...;
the Problems tab displays the description, location, and source file of the error.

Generally, error messages will look similar to this example.
Solving errors
Immediately after you run your project, OPL checks for errors that prevent the solver from running. If such errors are found, one or more error messages will be displayed in the Problems tab.