Introduction to Oracle ____oracle

What is ORACLE

 

Oracle database system is one of the most popular database of client/server (client/server) or b/s architecture, which is provided by Oracle Corporation (Oracle), a group of software products based on distributed database.

ORACLE is typically used in database products for large systems.

ORACLE database is the most widely used database management system in the world, as a general database system, it has complete data management function; As a relational database, it is a complete relation product; As a distributed database, it realizes the distributed processing function.

ORACLE databases have the following characteristics:

(1) Support for multi-user, large-scale transaction processing

(2) Data security and integrity control

(3) Support Distributed data processing

(4) Portability

ORACLE Architecture 1. The database

 

Oracle databases are the physical storage of data. This includes (data file ORA or DBF, control file, online log, parameter file). In fact, the Oracle database concept is different from other databases, where the database is an operating system with only one library. Can be seen as Oracle and there is only one

Large database.

2. Examples

 

An Oracle instance (Oracle Instance) has a series of background processes (Backguound processes)

and memory structure (Memory structures). A database can have n instances. 3. Data file (DBF)

The data file is the physical storage unit of the database. The data in the database is stored in the table space,

is actually in one or more data files. A tablespace can consist of one or more data files, and a data file can only belong to one table space. Once a data file has been added to a table space, you cannot delete the file, and if you want to delete a data file, you can delete only the tablespaces it belongs to. 4. Table Space

 

A tablespace is a logical mapping of Oracle's related data files (ORA or DBF files) on a physical database. A database is logically divided into a number of table spaces, each containing a set of structures that are logically associated. Each database has at least one tablespace (called the system table space).

Each tablespace consists of one or more files on the same disk, which are called data files

(datafile). A data file can belong to only one table space.

Note: Table data, there is a user into a table space, and this table space will randomly put this

Some of the table data is placed in one or more data files.

Since Oracle's database is not a common concept, Oracle has the user and tablespace to manage and store the data. But the table is not a table space to query, but by the user to check. Because different users can create a table with the same name in the same table space. Here the distinction is the user.

5. The user

 

The user is created in the table space. Users can only see and manipulate their own tables after landing, ORACLE

Users are similar to MYSQL's database, and each application needs to create a user.