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.

The unit display appears orange for the properties in the settings for the physics interface, physics features, and materials that have invalid or inconsistent units or a different unit than expected. 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. In the case of a valid but unexpected unit, this message contains the deduced and expected units in the current unit system.

If an unexpected or inconsistent unit appears in a text field for a physical property, the COMSOL 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. A unit display that appears red contains a syntax error, which can be due to, for example, missing or misplaced parentheses.

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 a yellow triangle in the lower-left corner.

If a problem occurs when you build a node, the build continues if it is possible; otherwise, the build stops. Continuing means that geometric entities where the operation failed are skipped and the problems are reported as Error subnodes () under the operation node. The build process continues with remaining nodes in the meshing sequence.

When the building of the meshing sequence is completed, the error window appears to show the first error reported. If there are several errors, you have to inspect the sequence for nodes with a Warning status and corresponding Error nodes to find all errors. If a node has Warning status, the node’s icon is decorated with a yellow triangle in the lower-right corner (see Dynamic Nodes in the Model Builder).

In some cases, you get a Warning node () even though meshing completed successfully. This happens, for example, when geometric entities are much smaller that the desired mesh element size, and you should interpreted the warning as a hint that the geometry needs to be simplified to avoid an unnecessarily fine mesh.

If meshing cannot continue, all building stops and the node gets an Error status, which the program indicates by adding a red cross in the lower-right corner of the node’s icon. You find information about the error in an Error subnode () of the node where the error occurred. If the node is part of a sequence build, the build stops and the preceding node becomes the current node.

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.