This took me awhile to understand myself.
The Archive Server is where the physical Cad files such as Solidparts and assemblies are stored. The archive server program encrypts these so that they cannot be read whithout an Enterprise client of the correct version. The Archive server has a program that is always open in the background encrypting and decrypting the files as they are stored or requested to/from the server. For multi-site installations you can have multiple Archive Servers in different locations, or replicated archive servers.
The Database server is the part of the server that stores the SQL database. The SQL database has all the data that is not part of the archive server. This includes who has what file checked out, the history of transactions and versioning of the file, what workflow it is currently in... essentially all the meta data and it is in an SQL database in order to be able to have quick queries and searches. For most multi-site installations there will be one Database(SQL) server that everyone connects to.
Often times it is hard to tell the difference between the two particularly because due to the size of the company and setup of your servers the two 'servers' can be technically the same server. Our installation has both the Database server and Archive server on the same machine.
Hope that helps make things a little clearer.
Thank you so much for the explanation!
To add to Roberts explination there are 3 essential components to the server side of EPDM: the Archive Server, the SQL Server and the Database Server. These can all be on the same physical machine but they all have different tasks. Like Robert said the Archive Server contains all the data, but not the folder structure, permissions, variables or anything else. The SQL Server hosts a vault database with all this information as well as the license file. The component that is actually named the Database Server:
Is actually a task server that is responsible for notifications, XML exports, cold storage and replications. The naming scheme is a bit confusing but I hope this helps.
Hi Charley Saint,
Thank you for the add up info!