For the applications discussed in Exercise 2.1 what placement strategies are employed in implementing the associated services?.
What will be an ideal response?
We first consider the mapping to multiple machines (covering partitioning and replication strategies):
Web: Web page masters are held in a file system at a single server. The information on the web as a whole is
therefore partitioned amongst many web servers.
Replication is not a part of the web protocols, but a heavily-used web site may provide several servers
with identical copies of the relevant file system using one of the well-known means for replicating slowlychanging data (Chapter 15). HTTP requests can be multiplexed amongst the identical servers using the (fairly
basic) DNS load sharing mechanism described on page 169. In addition, web proxy servers support replication
through the use of cached replicas of recently-used pages and browsers support replication by maintaining a
local cache of recently accessed pages.
Mail: Messages are stored only at their destinations. That is, the mail service is based mainly on partitioning,
although a message to multiple recipients is replicated at several destinations.
Netnews: Each group is replicated only at sites requiring it.
In terms of caching (and proxies), web servers cooperate with Proxy servers to minimize network traffic and
latency. Responsibility for consistency is taken by the proxy servers - they check the modification dates of
pages frequently with the originating web server.
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In Outlook, a checklist that allows you to list what needs to be done and check the items off as they are completed is called a(n) ________
Fill in the blank(s) with correct word
A(n) ________ is a value that can be changed, rather than specific, defined criteria
Fill in the blank(s) with correct word
When you click the ________ button, the selected bullet moves and the corresponding shape changes to a subordinate shape
A) Move Up B) Promote C) Demote D) Move Down
Once a PivotTable report is created, it CANNOT be changed
Indicate whether the statement is true or false.