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- home/database/oracle Database Online Documentation 11g Release 2 (11.2)/Database administration
- http://docs.oracle.com/cd/E11882_01/server.112/e40540/intro.htm#CNCPT001
Oracle Database Introduction Schema
- In Oracle DB, a schema or schema object is a collection of logical data structures.
- Schema is a user-created data structure with multiple types, the most important of which are tables and indexes
- A schema object is a database object that has many database objects, such as profile or role, that are not schema objects
- Table: Describes entity entities; The table consists of a table name, a collection of columns, a column name, a column's data type, and the length of the data type; A table can also be a collection of rows, a column specifies the attributes of an entity, a row specifies an instance of an entity, and you can also set an integrity constraint on each column
- Index: An optional data structure that can be created in one or more columns on a table, so that it is independent (both logically and physically) relative to the data, which means that you delete the index and have no effect on applications
Data access
- Sql
- Querying data
- Insert, UPDATE, delete row
- Create, replace, modify, delete objects
- Control the database and its object access rights
- Ensure database consistency and integrity
Transaction management
- Transaction
- Atomic Nature
- All or Nothing
- Concurrency of data
- Use the lock mechanism to maintain
- Data consistency
- Dirty read: The data the user is reading is modified by another user but not submitted
- Read consistency: Reading consistency
Oracle Architecture
- One database server corresponds to one database and at least one instance
- Database: A collection of files for storing data that can exist independently from a DB instance
DB instance: A set of memory structures consisting of SGA and background processes that can exist independently of the database file
A database can be considered from a physical or logical point of view
- The physical structure of the data is visible to the operating system
- Logical structure only has meaning to the database
Database storage structure
- Physical storage structure
- Data files
- Control files
- Online Redo log File
- Some of the other files
- Logical storage structure
- Data blocks (relative to OS block)
- Area (extents)
- Segment (segments)
- Table Space (tablespaces)
- DB instance
- Process: A mechanism that can run a series of steps on the operating system
- Client process: Used to run application software code or Oracle Tools
- Background process: Used to run various programs, asynchronously using IO, and monitoring database processes to prevent increasing parallelism for improved performance and reliability
- Server process: Responsible for interacting with the client process and interacting with the database, allowing the database to complete client process requests
- Note: Oracle processes include server processes and background processes, and in most environments, Oracle processes and client processes run on different machines
- The memory structure of the instance
- System Global Area (SGA): A set of shared memory structures that contains control information for a DB instance
- Program Global Areas (PGA): is a memory area that has control information for a server or background process. For processes, access to the PGA is exclusive, with each server process and background process having their own PGA
Application and network architecture
- Application structure
- C
- Multitier (Multilayer)
- Soa
- Network structure
- Oracle Net Services: Is the interface of database and network communication Protocol, network communication protocol facilitates distributed processing and distributed database, and communication protocol defines the method of data transfer and reception on the network. Oracle NET Services supports all major network protocols, including TCP/IP, HTTP, FTP, and WebDAV
- Oracle NET: is a component of Oracle NET services that establishes and maintains network sessions for client programs and database servers. When a session is established, it exchanges information as a data couriers, in the client program and the database server, and it exists on each computer in the network.
- Oracle Net Listener (called the Listener): is a standalone process that runs on the database server or elsewhere in the network, and the client program can send a connection request to the listener to process these requests for the database server. When the connection is established, the client and the database can communicate directly
- In most cases, the method of configuring the database service request for the client has
- Dedicated server architecture (dedicated server architecture): Each client process connects to a dedicated server process that is not shared, and each new session is assigned a dedicated server process
- Shared server architecture: The database uses a shared pool of shared processes to serve multiple sessions, and the client process communicates with the scheduler.
1 Introduction to Oracle database reading notes
