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Query [message #20728] Sun, 16 June 2002 07:51 Go to next message
Ragav
Messages: 4
Registered: April 2002
Junior Member
i have a query regarding the execution of sql query by an oracle database.i want the complete set of background process that is happening in oracle as soon as we enter a query in the sql*plus.i just want anyone to help me reg. this
Re: Query [message #20730 is a reply to message #20728] Sun, 16 June 2002 11:55 Go to previous message
Mahesh Rajendran
Messages: 10707
Registered: March 2002
Location: oracleDocoVille
Senior Member
Account Moderator
Hope this helps you.
from the Oracle Documentation

An Example of How Oracle Works
The following example illustrates an Oracle configuration where the user and associated server process are on separate machines (connected via a network).

1. An instance is currently running on the computer that is executing Oracle (often called the host or database server).

2. A computer running an application (a local machine or client workstation) runs the application in a user process. The client application attempts to establish a connection to the server using the proper Net8 driver.

3. The server is running the proper Net8 driver. The server detects the connection request from the application and creates a (dedicated) server process on behalf of the user process.

4. The user executes a SQL statement and commits the transaction. For example, the user changes a name in a row of a table.

5. 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.

6. The server process retrieves any necessary data values from the actual datafile (table) or those stored in the system global area.

7. The server process modifies data 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.

8. If the transaction is successful, the server process sends a message across the network to the application. If it is not successful, an appropriate error message is transmitted.

9. Throughout this entire procedure, the other background processes run, watching for conditions that require intervention. In addition, the database server manages other users' transactions and prevents contention between transactions that request the same data.

10. These steps describe only the most basic level of operations that Oracle performs.

See Also:
Chapter 8, "Process Architecture" for more information about Oracle configuration.
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