The following example describes Oracle Database operations at the most basic level.
This illustrates an Oracle Database configuration where the user and associated server
process are on separate computers, connected through a network.
1. An instance has started on the computer running Oracle Database, often called the
host or database server.
2. A computer running an application (a local computer or client workstation) runs
an application in a user process. The client application attempts to establish a
connection to the server using the proper Oracle Net Services driver.
3. The server is running the proper Oracle Net Services 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 runs 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 (an SGA
component) for any shared SQL area that contains a similar SQL statement. If a
shared SQL area is found, then the server process checks the user's access
privileges to the requested data, and the existing shared SQL area is used to
process the statement. If not, then a new shared SQL area is allocated for the
statement, so it can be parsed and processed.
6. The server process retrieves any necessary data values, either from the actual
datafile (table) or those stored in the SGA.
7. The server process modifies data in the system global area. The database writer
process (DBWn) writes modified blocks permanently to disk when doing so is
efficient. Because the transaction is committed, the log writer process (LGWR)
immediately records the transaction in the redo log file.
8. If the transaction is successful, then the server process sends a message across the
network to the application. If it is not successful, then an 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.
This illustrates an Oracle Database configuration where the user and associated server
process are on separate computers, connected through a network.
1. An instance has started on the computer running Oracle Database, often called the
host or database server.
2. A computer running an application (a local computer or client workstation) runs
an application in a user process. The client application attempts to establish a
connection to the server using the proper Oracle Net Services driver.
3. The server is running the proper Oracle Net Services 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 runs 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 (an SGA
component) for any shared SQL area that contains a similar SQL statement. If a
shared SQL area is found, then the server process checks the user's access
privileges to the requested data, and the existing shared SQL area is used to
process the statement. If not, then a new shared SQL area is allocated for the
statement, so it can be parsed and processed.
6. The server process retrieves any necessary data values, either from the actual
datafile (table) or those stored in the SGA.
7. The server process modifies data in the system global area. The database writer
process (DBWn) writes modified blocks permanently to disk when doing so is
efficient. Because the transaction is committed, the log writer process (LGWR)
immediately records the transaction in the redo log file.
8. If the transaction is successful, then the server process sends a message across the
network to the application. If it is not successful, then an 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.
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