The eCat tab contains an indicator that indicates the state of the background indexing service. The indicator resides in the top right corner of the "Models" section.
When the indicator is green, the file database is up-to-date. This means that all the files are indexed and can be found and used in the catalog.
When the indicator is red the service is doing work and therefore has some files still unprocessed. The service can be busy indexing local or remote files. The tooltip on the indicator shows which one it is processing. You can view the tooltip by hoovering the mouse curson over the indicator.
When you, for example, copy a file into a folder that is listed as eCat folder in the application options, the indicator turns red for a second or two and turns back green when the file is processed.
If the indicator disappears it means that the connection to the indexing service is lost. This should not happen in the during normal use. The situation can be tried to be remedied by restarting the application or the whole computer.