COMSOL Multiphysics reports problems of two types: errors and warnings.

Errors prevent the program from completing a task. For errors, a COMSOL Error window appears with a brief error description and, in some cases, an Open Log File button for additional information. Under the node where the error occurred there is, in most cases, also an Error subnode () that contains an error message that generally provides additional information. Also, for many error types, the icon for the node where the error occurred appears with a red cross in the lower-right corner. For some errors there is also a link to more diagnostic information on the COMSOL website.

It is possible to open and postprocess models that include functionality that you have blocked or that your license does not include. Nodes with functionality that requires a license for a product that is blocked or not available get a License Error subnode (), where you find information about the missing but required product license. Unless you disable or remove such nodes, it is not possible to re-solve such models.

Warnings are problems that do not prevent the completion of a task but that might affect the accuracy or other aspects of the model. Warnings typically appear in the Log window (). The warning message also appears as a Warning subnode () under the node from which the warning was sent.

An inconsistent unit can occur by summing terms with units that represent different physical quantities, such as 273[K]+3[ft]. A tooltip displays a message at the corresponding field.

If an unexpected or inconsistent unit appears in a text field for a physical property, the COMSOL Multiphysics software ignores the unit and uses the numerical value, including an SI prefix if present, as the input to the model. For example, in a text field for density using SI units, the software interprets 2930[K] as 2930 kg/m3 and 2930[mK] as 2.930 kg/m3.

If an error occurs when you build a node, the build stops. The node with the problem then gets an Error subnode () that contains the error message. Also, the node’s icon displays with a red cross in the lower-left corner.

After a successful build of a node, a warning message can sometimes display as a Warning subnode (). If a warning message exists, the node’s icon displays with an orange triangle in the lower-right corner.

Information () and Warning () nodes can occur even though meshing completed successfully. They serve as an indication that something can turn into a problem when running the solver or to get accurate result. Error nodes () always indicate that an operation has failed, either for individual geometric entities or that the build failed completely. For more information, see Information, Warning, and Error Nodes for Meshing Operations.

Issues encountered when running a solver or generating a mesh are treated in two different ways depending on if it is possible to avoid the problem and continue the operation or if the operation must be stopped. In the first case, a Warnings node () appears under the node in the model tree that caused the problem. In the second case, an Error node () appears under the node in the model tree that caused the error.

A Warnings node () can also appear under a Compile Equations node if some input to the solvers uses inconsistent units, for example.

For things like empty plots, Warnings nodes () can appear in the Results branch during postprocessing. However, you do not get any warnings in these cases: