Below are 4 practice interview questions based on 'instances' concept of Database Servers.
In Very Simple Terms, Can you describe what is actually a Database Server instance?
Every Database Server Instance is a complete server by itself with own set of databases, login credentials etc. A single machine that has many server instances can be logically compared to multiple machines with their own Database Server installations.
Will executing/operating more than one Database Server instances on a single machine affect performance of applications adversely?
More than one instance would require more memory and processor related resources than single instance on the same machine. But, more than one instance can speed up applications by allowing multiple applications to operate on multiple instances of Database Server simultaneously.
What could be the role of a server administrator to keep up the performance of machine with multiple instances?
The server administrator is responsible for striking a balance between number of allowed SQL instances and system's hardware resources.
Can databases on multiple instances have same names?
Yes. Any database on an instance is completely local to that database.