The communication from Virtual DataPort to the external database has to be stable. If at some point, the communication to the external database is not possible due to some network problem, the execution engine cannot start to process any query until the communication is re-established.
The connection will be re-established once the network issue is resolved and there is no limit for the retries.
For more information, you can take a look at the **[Storing the Metadata on an External Database](https://community.denodo.com/docs/html/browse/8.0/en//vdp/administration/server_configuration/storing_catalog_on_external_database/storing_catalog_on_external_database#storing-the-metadata-on-an-external-database)** section of the Virtual DataPort Administration Guide.
Hope this helps!