Copyright  Oracle Corporation, All rights reserved. 1 Oracle Architectural Components

1-2 Copyright  Oracle Corporation, All rights reserved. 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 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

1-3 Copyright  Oracle Corporation, All rights reserved. The Oracle Server Server Application/ network server Users Oracle server

1-4 Copyright  Oracle Corporation, All rights reserved. Connecting to a Database User Client Server Server process Oracle server User process

1-5 Copyright  Oracle Corporation, All rights reserved. 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 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

1-6 Copyright  Oracle Corporation, All rights reserved. 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 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

1-7 Copyright  Oracle Corporation, All rights reserved. Oracle Instance Background processes An Oracle instance: Is a means to access an Oracle database Always opens one and only one database An Oracle instance: Is a means to access an Oracle database Always opens one and only one database Instance SGA

1-8 Copyright  Oracle Corporation, All rights reserved. Oracle Database Control files Redo log files Data files Password file Parameter file Archived log files Database

1-9 Copyright  Oracle Corporation, All rights reserved. Database Other Key Physical Structures Archived log files Password file Parameter file

1-10 Copyright  Oracle Corporation, All rights reserved. User process Server process Processing a Query Parse Statement OK Handle Execute OK Handle Fetch Results SELECT * FROM emp ORDER BY ename; SELECT * FROM emp ORDER BY ename;

1-11 Copyright  Oracle Corporation, All rights reserved. The Shared Pool 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 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 Shared pool Library cache Data dictionary cache

1-12 Copyright  Oracle Corporation, All rights reserved. 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 Number of buffers defined by DB_BLOCK_BUFFERS Size of a buffer based on DB_BLOCK_SIZE Stores the most recently used blocks

1-13 Copyright  Oracle Corporation, All rights reserved. Program Global Area (PGA) Not shared and not writable Contains – Sort area – Session information – Cursor state – Stack space Not shared and not writable Contains – Sort area – Session information – Cursor state – Stack space PGA Server process

1-14 Copyright  Oracle Corporation, All rights reserved. Instance SGA Shared pool Library cache Redo log buffer Database buffer cache Data dictionary cache UPDATE emp SET sal=sal*1.1 WHERE empno=7369 UPDATE emp SET sal=sal*1.1 WHERE empno=7369 Processing a DML Statement 1 Server process Control files Redo log files Data files Database

1-15 Copyright  Oracle Corporation, All rights reserved. Rollback Segment DML statement Old image New image Rollback segment Table

1-16 Copyright  Oracle Corporation, All rights reserved. Redo Log Buffer Size defined by LOG_BUFFER Records changes made through the instance Used sequentially Circular buffer Size defined by LOG_BUFFER Records changes made through the instance Used sequentially Circular buffer

1-17 Copyright  Oracle Corporation, All rights reserved. Instance SGA Shared pool DBWR Database buffer cache Database Writer (DBWR) Control files Redo log files Data files

1-18 Copyright  Oracle Corporation, All rights reserved. Instance SGA Shared pool Redo log buffer LGWR Log Writer (LGWR) Control files Redo log files Data files

1-19 Copyright  Oracle Corporation, All rights reserved. Shared pool Redo log buffer LGWR Control files Redo log files Data files Database COMMIT Processing Server process 1 2 User process 3 Database buffer cache 4 SGA Instance

1-20 Copyright  Oracle Corporation, All rights reserved. Instance SGA Shared pool DBWRLGWR Database Control files Data files Redo log files User process Server process PGA Summary Password file Archived log files Parameter file