You can get an “error unmarshalling return” error when you try to connect to a VDP Server from a Virtual DataPort Administration Tool that is from a different version or has a different update installed. All the VDP tools must be in the same version and update as the VDP server to avoid inconsistency problems like this.
An example of this error is the following:
error unmarshalling return; nested exception is: java.io.InvalidClassException: com.denodo.vdb.vdbinterface.common.clientResult.vo.descriptions.database.WidgetDescVO; local class incompatible: stream classdesc serialVersionUID = -8512420786864834667, local class serialVersionUID = -2263184989842310482
The above error nests an exception that depends on the content of the virtual database you are connecting to.
In this case, it is a specific error for a Widget component, but the start of the message error unmarshalling return is always the same when having installed different versions of the VDP Admin Tool and the VDP Server.
Below you can see a screenshot of this error when connecting from the VDP admin tool to a VDP server with a different update:
To avoid this kind of error when you install an update, make sure to update all your installations.
For Denodo 6 and newer versions, instead of getting this error a warning alerting that the updates installed on the server and on the client-side are different will be displayed. In these versions, some of the functionality of the VDP Administration tool will be available depending on the different updates installed.