An instance is currently running on the computer that is executing Oracle called database server.

A computer is running an application (local machine) runs the application in a user process.

 

• The client application attempts to establish a connection to the server using the proper Net8 driver. 
• When the oracle server detects the connection request from the client it’s check client authentication, if authentication pass the oracle server creates a (dedicated) server process on behalf of the user process. 
• When the user executes a SQL statement and commits the transaction. For example, the user changes a name in a row of a table. 
• The server process receives the statement and checks the shared pool for any shared SQL area that contains an identical SQL statement. 
• If a shared SQL area is found, the server process checks the user's access privileges to the requested data and the previously existing shared SQL area is used to process the statement; if not, a new shared SQL area is allocated for the statement so that it can be parsed and processed. 
• The server process retrieves any necessary data values from the actual datafile or those stored in the system global area. 
• The server process modifies data block in the system global area. 
• The DBWn process writes modified blocks permanently to disk when doing so is efficient. Because the transaction committed, the LGWR process immediately records the transaction in the online redo log file.
• If the transaction is successful, the server process sends a message across the network to the application. I
• f it is not successful, an appropriate error message is transmitted. Throughout this entire procedure, the other background processes run, watching for conditions that require intervention.