Question 11 :
Data replication is favored where most process requests are read-only and where the data are relatively static.
Question 12 :
The cost to perform a snapshot refresh may depend on whether the snapshot is simple or complex.
Question 13 :
The semijoin approach saves network traffic.
Question 14 :
In a semijoin, only the joining attribute is sent from one site to another, and then only the required rows are returned.
Question 15 :
The problem of concurrency control is more complex in a distributed database.