DDBMS must ensure that no two sites create a database object with the same name. One solution to this problem is to create a central name server. What are the disadvantages with this approach? Propose an alternative approach that overcomes these disadvantages.

Question

What will be an ideal response?

Answer 1

Problems with the central name server, which has the responsibility for ensuring uniqueness of all
names in the system, are:
? loss of some local autonomy
? performance problems, if the central site becomes a bottleneck
? low availability, if the central site fails, the remaining sites cannot create any new database objects.
An alternative solution is to prefix an object with the identifier of the site that created it. For example,
a relation BRANCH created at site S 1 might be named S1.BRANCH. Similarly, we would need to be
able to identify each fragment and each of its copies. Thus, copy 2 of fragment 3 of the branch relation
created at site S 1 might be referred to as S1.BRANCH.F3.C2. However, this results in loss of
distribution transparency.
An approach that resolves the problems with both these solutions uses aliases for each database
object. Thus, S1.BRANCH.F3.C2 might be known as local_branch by the user at site S 1 . The
DDBMS has the task of mapping aliases to the appropriate database object.