Hosts sensors should not consume DBmarlin licences. However, during the start-up of a host sensor, the free licence count is inadvertently checked. That means that if you have created and started the same number of instances as licences, you will not be able to start any hosts. The workaround is to stop a database instance sensor, then you will be able to start any host sensors. Once they are all running, then restart the one database instance agent that you closed. In that way all host and database sensors can be started. The regular checks to ensure that the licence counts are not exceeded to not have this error, so running host sensors will not then be shut down.