Solr is implemented as a self-contained web application, separate from VIVO. At most VIVO sites, Solr and VIVO run on the same machine, in the same instance of Tomcat, but this is not the only possible configuration. It is possible to put Solr in a different servlet container or even host Solr on a different computer from VIVO.
In a typical VIVO installation, Solr is hidden behind VIVO, and the users cannot do not access it directly. In general, they don't know that Solr exists as an application. Before releasing VIVO to the public, a site admin should take steps to secure their Solr installation to ensure only administrators and the VIVO application can modify the search index.
How does VIVO use Solr?
VIVO uses the Solr search engine in two ways: