About Oracle Databases

What does the Oracle database do?

Oracle database is the same as other databases, it is to save the data, and can go to query, modify, delete, etc.
The difference between Oracle and other data is that its complex mechanisms ensure that the data is not lost or corrupted when the database server suddenly breaks down.

Architecture of Oracle Database

Oracle databases include Oracle database servers and clients. 

Oracle Database server:
Oracle Server is an object-relational database management system. It provides an open, comprehensive, and integrated approach to information management. Each server consists of an Oracle DB and an instance of Oracle server. It has site autonomy (site Autonomy) and provides a transparent mechanism for data storage, which enables data storage transparency. Each Oracle database corresponds to a unique instance name sid,oracle after the database server is started, there are generally at least a few users: Internal, which is not a real user name, but an alias for the SYS user with the SYSDBA priority, It is used by the DBA user to complete the management tasks of the database, including starting and shutting down the database; Sys, which is a DBA user name with the largest database operation permission; System, which is also a DBA user name, second to the Sys user. 

Client:
as a database user operator, consisting of applications, tools, and sql* net, when a user operates a database, it must be connected to a server, which is called a local database. In the network environment, the DB on the other server is called the remote db. When a user accesses data on a remote DB, a database chain must be established. 

the architecture of an Oracle database includes a physical storage structure and a logical storage structure. Because they are separated, they do not affect the access to the logical storage structure when managing the physical storage structure of the data. 

1. Logical Storage Structure
It consists of at least one Tablespace and database schema object. Here, a pattern is a collection of objects, whereas a schema object is a logical structure that directly references database data. Schema objects include structures such as tables, views, sequences, stored procedures, the same word, indexes, clusters, and database chains. Logical storage structures include table spaces, segments, and scopes that describe how to use the physical space of a database. The model objects and relationships form the relational design of the database. 

Block : is the smallest unit of the database for UO operations, and it is not a concept with the operating system's block. Instead of requesting data in the block of the operating system, the Oracle database is in multiple Oracle database blocks. 

segment (Segment): is a logical storage structure of a specified type in a tablespace that consists of one or more scopes that occupy and grow storage space. 

These include:
data segment: Used to store table data;. 
Index segment: Used to store table index;
Temporary segment: Used to store intermediate results;
Rollback Segment: Resumes a transaction when an exception occurs. 
scope (Extent): Is the logical unit of database storage space allocation, a range consists of a number of contiguous blocks of data, the scope of which is assigned by the segment, the first range assigned is called the initial range, and the later assigned range is called the Delta range. 

The advantages are:
High Availability
Strong Scalability
Strong data Security
Strong stability

About Oracle Databases