You need to connect server to existing farm in sharepoint. If due to some issue, you disconnected web front-end server from sharepoint farm. After issue resolution, you need to connect web front-end server back to exisiting server farm again.
sharepoint administration service
By time workflow content grow high which will impact performance. So as to improve performance of workflow for sharepoint site containing nintex workflow, we can move nintex database from default all in one content to a dedicated nintex database. Moving nintex database to dedicated content database from common db is called split database.