Ontolica Preview database needs to be installed to store first-page-preview images of documents and Web pages indexed by SharePoint. This database will also be used to temporarily store (cache) preview images from live conversion when the full-document-preview option is selected. If the first-page-preview option is not preferred then the Ontolica Preview database does not need to be installed.
To install the database go to Central Administration > General Application Settings > Manage Ontolica Modules > Manage Ontolica Preview Database page. Type the name of your SQL server, user name and password. The account, associated with provided credentials, needs to have the right to create databases on the selected database server instance. Click the Connect button and when connected click the Install button to create the database.