Detailed process of user interaction with OracleDB

Detailed process of user interaction with OracleDB

Interaction with Oracle DB

The following example describes the Oracle database operations at the most basic level. This example shows an Oracle DB configuration in which the user and the associated server processes run on different computers connected through the network.

1. Start an instance on a node with Oracle DB installed (usually known as a "host" or "Database Server.

2. the user starts an application that derives a user process. The application tries to establish a connection with the server (this connection may be a local connection, a client/server connection, or a layer-3 connection from the middle layer ).

3. The server runs a listener with the corresponding Oracle Net Services processing program. The listener detects the connection request sent by the application and creates a dedicated server process that represents the user process.

4. the user runs a dml SQL statement and submits the transaction processing. For example, you can change the customer address in the table and submit the change.

5. The server process receives the statement and checks whether the shared SQL area contains the same SQL statement in the Shared Pool (an SGA component. If the shared SQL area is found, the server process checks the user's access permissions to the requested data and processes the statement using the existing shared SQL area. If the shared SQL area is not found, a new shared SQL area is allocated to the statement for syntax analysis and processing.

6. The server process retrieves any required data values from the values stored in the actual data file (table) or database buffer cache.

7. The server process modifies the data in the SGA. Because the transaction processing is committed, the log write process (LGWR) immediately records the transaction processing to the redo log file. The database write process (DBWn) permanently writes the modified block to the disk when the execution efficiency is high.

8. If the transaction is processed successfully, the server process will send a message to the application over the network. If the transaction fails to be processed, an error message is sent.

9. during the entire process, other background processes are running at the same time to monitor whether intervention is required. In addition, the database server manages transactions processed by other users and prevents contention between transactions that request the same data.