What is the difference between metadata and data dictionary?

Metadata is defined as data about the data. But, Data dictionary contain the information about the project information, graphs, abinito commands and server information.

What are the tools available for ETL?

Following are the ETL tools available:
 Informatica
Data Stage
Oracle
Warehouse Builder
Ab Initio
Data Junction

What are the approaches used by Optimizer during execution plan?

There are two approaches:
 Rule Based
Cost Based

What is Execution Plan?

Execution Plan is a plan which is used to the optimizer to select the combination of the steps.

What is the goal of Optimizer?

The goal to Optimizer is to find the most efficient way to execute the SQL statements.

What is defined as Partial Backup?

A Partial backup in an operating system is a backup short of full backup and it can be done while the database is opened or shutdown.

Can we take backup when the database is opened?

No, We cannot take full backup when the database is opened.