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Function is an algorithm which can be used any where in the program when required

Structure: Initially (in C) a structure was used to bundle different type of data types together to perform a particular functionality. But C++ extended the structure to contain functions also. The major difference is that all declarations inside a structure are by default public.
Class: Class is a successor of Structure. By default all the members inside the class are private.

Oracle Real Application Clusters (RAC) is a software component we can add to a high-availability solution that enables users on multiple machines to access a single database with increased performance. RAC comprises two or more Oracle database instances running on two or more clustered machines and accessing a shared storage device via cluster technology. To support this architecture, the machines that host the database instances are linked by a high-speed interconnect to form the cluster. Oracle RAC offers features in the following areas:

- Scalability

- Availability

- Load balancing

- Failover

Star schema: A highly de-normalized technique. A star schema has one fact table and is associated with numerous dimensions table and depicts a star.

Snow flake schema: The normalized principles applied star schema is known as Snow flake schema. Every dimension table is associated with sub dimension table.

Differences:

- A dimension table will not have parent table in star schema, whereas snow flake schemas have one or more parent tables.

- The dimensional table itself consists of hierarchies of dimensions in star schema, where as hierarchies are split into different tables in snow flake schema. The drilling down data from top most hierarchies to the lowermost hierarchies can be done.

Generating random passwords in PHP can be done in multiple ways depending on how much security the application demands:-

Md5 function can be passed one parameter as uniqid() function which in turn generates a random number. Passing the parameter as TRUE in uniqid() adds additional uniqueness.

<?php
   $passwd = md5(uniqid(rand(), true));
   Echo $passwd;
?>

One of the main causes of congestion is that traffic is often busy. If hosts could be made to transmit at a uniform rate, congestion would be less common. Another open loop method to help manage congestion is forcing the packet to be transmitted at a more predictable rate. This is called traffic shaping.

The backup strategies that are provided by Oracle are as follows:

- Logical backup using Exports and import.

- Physical file system backup

- RMAN Recovery Manger which is also known as incremental files system backup.