1.Oracle Database Overview

Oracle Database Overview

1.1Oracle structure Diagram

1.1 How to access the database

A. this machine accesses the IPC UDP protocol directly via sock(socket) , does not require network

B. establishing a connection to an Oracle server via TCP

1.2 accessing the remote database

A. Configure Tnsnames.ora files such as:

ORCL =

(DESCRIPTION =

(ADDRESS = (PROTOCOL = TCP) (HOST = dbserver) (PORT = 1521))

(Connect_data =

(SERVER = dedicated)

(service_name = ORCL)

)

)

W_ORCL =

(DESCRIPTION =

(ADDRESS = (PROTOCOL = TCP) (HOST = 192.168.1.1) (PORT = 1521))

(Connect_data =

(SERVER = dedicated)

(service_name = ORCL)

)

)

B. direct use without configuration such as:

Sqlplus sys/[email protected]: 1521/ORCL as SYSDBA;

1.3 A statement execution procedure

A. The user process executes a query statement such as select * from EMP; The user has established a connection with the server process and stored the user process information in PGA of the UGA the. The statement is passed to the instance after the PGA process, and the shared pool in the instance is responsible for processing the statement. Library buffers to determine how statements are analyzed --- soft or hard analysis.

B. prepare to execute the statement according to the implementation plan obtained by the CBO.

C. in which table space is the object in the query statement stored, and in which block is the specified row placed? This information is obtained from the data dictionary buffers. (The data dictionary is in a shared cache component.)

D. start execution to determine whether the data buffer cache is required for caching blocks. If the results of the desired rows are returned to the user in memory-read data, the user sees the result of the execution, and if there is no cache, the server process reads the block from the disk into the data buffer cache, andtheundo the cache block mirrors the block and then reads the data in the image to get a record of the row, and the user sees the result of the execution.

1.Oracle Database Overview