It depends on the type of business that demands a cloud setup. Suppose if the subscription on a public cloud for an application that is to be deployed on OS images is proving to be more costly then to buy some new datacenters and maintain them. Then obviously the a private cloud has to be setup instead of a public cloud. This public clouds follow utility billing methodology as electricity bill for example.

The hypervisor is a virtual machine monitor (VMM) that manages resources for virtual machines. The name hypervisor is suggested as it is a supervisory tool for the virtual machines. There are mainly two types of hypervisors :

- Type-1: the guest Vm runs directly over the host hardware, e.g Xen, Hyper-V, VmWare ESXi

- Type-2: the guest Vm runs over hardware through a host OS, e.g Kvm, Oracle virtualbox

Cloud computing is a metaphor used for internet. It provides on-demand access to virtualized IT resources that can be shared by others or subscribed by you. It provides an easy way to provide configurable resources by taking it from a shared pool. The pool consists of networks, servers, storage, applications and services.

Data warehouse

- It is a decision support database system for the purpose of organizational needs. 

-It is non volatile, integrated and time variant collection of data

Operational Data Stage

- It is an integrated collection of information. 

-It can contain 90 days of information at maximum.

-ODS supports dynamic data.

Cascade:

- Cascade process involves taking values from various other prompts.

- The result is a single report.

- The result is used when a criteria is to be implemented.

Drill Through:

- Drill Through process is implemented when navigation from summary to detailed information.

- Drill Through has a parent and a child report.

- Data of another report can be seen based on the current details of data.

- Agglomerative Hierarchical clustering method allows the clusters to be read from bottom to top and it follows this approach so that the program always reads from the sub-component first then moves to the parent. Whereas, divisive uses top-bottom approach in which the parent is visited first then the child. 

- Agglomerative hierarchical method consists of objects in which each object creates its own clusters and these clusters are grouped together to create a large cluster. It defines a process of merging that carries on till all the single clusters are merged together into a complete big cluster that will consists of all the objects of child clusters. Whereas, in divisive the parent cluster is divided into smaller cluster and it keeps on dividing till each cluster has a single object to represent.

At the time of updating the data warehouse, a lookup table is used. When placed on the fact table or warehouse based upon the primary key of the target, the update is takes place only by allowing new records or updated records depending upon the condition of lookup.

The materialized views are aggregate tables. It contains summarized data. For example, to generate sales reports on weekly or monthly or yearly basis instead of daily basis of an application, the date values are aggregated into week values, week values are aggregated into month values and month values into year values. To perform this process aggregate function is used.

The primary keys of entity tables are the foreign keys of dimension tables.

The Primary keys of fact dimensional table are the foreign keys of fact tablels.