Concurrent Access to the News Database

  The news cache has to support simultaneous access from multiple clients. Hence it is necessary that multiple instances of the News Cache are running which access the News Cache's news database. This may be achieved by either using a single process for each client or by using a threaded cache server. We will discuss the pros and cons of this topic in section 6.1 in more detail. However, both solutions have to support concurrent access to the news database.

Since concurrent access to the news cache database has to be provided, mutual exclusion has to be guaranteed for update requests. Whenever an instance of the News Cache needs to update the news database, the news database has to be exclusively locked for the update operation. We will discuss this problem in detail in section 6.5.