How Oracle processes a query

 How oracle processes a query
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 1)The user executes a SQL statement and commits the transaction. For example,
 the user changes a name in a row of a table.
 2)The server process receives the statement and checks the shared pool for any
 shared SQL area that contains a similar 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 it can
 be parsed and processed.
 3)The server process retrieves any necessary data values from the actual datafile
 (table) or those stored in the system global area.
 4)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 is committed, the LGWR process immediately records the
 transaction in the online redo log file.
 5)If the transaction is successful, the server process sends a message across the
 network to the application. If it is not successful, an error message is
 transmitted.