1. Oracle Architectural Components

2. Objectives
Listing the structures involved in connecting a user to an Oracle server
Listing the stages in processing a query
Listing the stages in processing a DML statement
Listing the stages in processing COMMITS

3. The Oracle Server Application/ network server Server Users

4. Connecting to a Database
Server process
Client
Server
Oracle server
User process
User

5. User Process Runs on the client machine
Is spawned when a tool or an application is invoked
Runs the tool or application (SQL*Plus, Server Manager, Oracle Enterprise Manager, Developer/2000)
Includes the User Program Interface (UPI)
Generates calls to the Oracle server

6. Server Process Runs on the server machine (host)
Services a single user process in the dedicated server configuration
Uses an exclusive PGA
Includes the Oracle Program Interface (OPI)
Processes calls generated by the client
Returns results to the client

7. Oracle Instance An Oracle instance:
SGA
Background processes
An Oracle instance:
Is a means to access an Oracle database
Always opens one and only one database

8. Oracle Database Database Control files Parameter file Data files
Redo log files
Password file
Archived log files
Database

9. Other Key Physical Structures
Parameter file
Password file
Archived log files
Database

10. Processing a Query Parse Execute Fetch User process Server process
Statement
Handle
Execute
SELECT *
FROM emp
ORDER BY ename;
Handle
Fetch OK OK
Results
User process
Server process

11. The Shared Pool Size defined by SHARED_POOL_SIZE
Library cache
Data dictionary cache
Size defined by SHARED_POOL_SIZE
Library cache contains statement text, parsed code, and an execution plan
Data dictionary cache contains table and column definitions and privileges

12. Database Buffer Cache Number of buffers defined by DB_BLOCK_BUFFERS
Size of a buffer based on DB_BLOCK_SIZE
Stores the most recently used blocks

13. Program Global Area (PGA)
Server process
Not shared and not writable
Contains
Sort area
Session information
Cursor state
Stack space

14. Processing a DML Statement3
UPDATE emp
SET sal=sal*1.1
WHERE empno=7369
Instance
SGA
Shared pool
Library cache
Redo log buffer
Database buffer cache
Data dictionary cache 4 5
Server process 2 1
Control files
Redo log files
Data files
Database

15. Rollback Segment Old image New image Table Rollback segment
DML statement

16. Redo Log Buffer Size defined by LOG_BUFFER
Records changes made through the instance
Used sequentially
Circular buffer

17. Database Writer (DBWR)
Instance
SGA
Shared pool
DBWR
Database buffer cache
Data files
Control files
Redo log files

18. Log Writer (LGWR) Instance SGA Shared pool Redo log buffer LGWR
Data files
Control files
Redo log files

19. COMMIT Processing 1 4 3 2 Server process User process Instance SGA
Shared pool
Server process
Database buffer cache
Redo log buffer 4 2 3
LGWR
User process
Control files
Redo log files
Data files
Database

20. Summary Instance SGA Database Server process User process Shared pool
DBWR
LGWR
Server process
PGA
User process
Parameter file
Control files
Data files
Archived log files
Redo log files
Password file
Database