Explain the components of physical database structure of Oracle database?

Oracle database is comprised of three types of files. One or more datafiles, two are more redo log files, and one or more control files.

Explain the components of logical database structure of Oracle database? 

There are tablespaces and database's schema objects. 

Explain a tablespace? 

A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to grouped related logical structures together.

Explain SYSTEM tablespace and when is it created?

Every Oracle database contains a tablespace named SYSTEM, which is automatically created when the database is created. The SYSTEM tablespace always contains the data dictionary tables for the entire database.

Explain the relationship among database, tablespace and data file.

Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace.

Explain schema?

A schema is collection of database objects of a user.

Explain Schema Objects?

Schema objects are the logical structures that directly refer to the database's data. Schema objects include tables, views, sequences, synonyms, indexes, clusters, database triggers, procedures, functions packages and database links.

Can objects of the same schema reside in different tablespaces? 

Yes. 

Can a tablespace hold objects from different schemes? 

Yes.

Explain Oracle table?

A table is the basic unit of data storage in an Oracle database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.

Explain an Oracle view?

A view is a virtual table. Every view has a query attached to it. (The query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)

Do a view contain data?

Views do not contain or store data.

Can a view based on another view?

Yes.

Explain the advantages of views?

- Provide an additional level of table security, by restricting access to a predetermined set of rows and columns of a table.
- Hide data complexity.
- Simplify commands for the user.
- Present the data in a different perspective from that of the base table. - Store complex queries.

Explain an Oracle sequence?

A sequence generates a serial list of unique numbers for numerical columns of a database's tables.

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