User interaction with Oracle DB specific process

Interacting with Oracle DB
The following demo sample describes Oracle DB operations from the most significant level. This demo sample illustrates an Oracle DB configuration in which the user and the associated server processes are performed on different computers that are connected over a network.
1. An instance is started on a node that has Oracle DB installed (often referred to as a "host" or "Database Server").
2. The user launches an application that derives a user process. The application attempts to establish a connection to the server (this connection may be a local connection, a client/server connection, or a three-tier connection from the middle tier).
3. Server executes a listener with the corresponding Oracle Net Services handler. The listener detects connection requests made by the application and creates a private server process that represents the user process.
4. The user executes a DML-type SQL statement and commits the transaction. For example, the user changes the customer address in the table and submits the change.
5. The server process receives the statement and checks if there is a shared SQL region in the shared pool (an SGA component) that includes the same SQL statement. Assuming a shared SQL zone is found, the server process checks the user's access to the requested data and processes the statement using an existing shared SQL region. Assuming a shared SQL region is not found, the statement is assigned a new shared SQL region to parse and process the statement.

6. The server process retrieves whatever data value is required from the actual data file (table) or value stored in the database buffer fast cache.
7. The server process changes data in the SGA. Because the transaction is committed, the log write process (LGWR) immediately logs the transaction to the Redo log file. The database write process (DBWN) will permanently write the modified block to disk when it is running at high efficiency.
8. Assuming the transaction is successful, the server process sends a message over the network to the application. If the transaction is unsuccessful, an error message is sent.
9. Throughout the process, other background processes are executed at the same time to monitor for situations in which there is a need for intervention. In addition, database server manages the transactions of other users and prevents contention between transactions that request the same data.

User interaction with Oracle DB specific process