Oracle Architecture;
Process:
1. Client processes - To run the application or Oracle tool code (e.g. Sqlplus, toad, sqldeveloper).
2. Oracle processes - To run the Oracle (sql and plsql) Code.
(I) Background Process - To cleaning up, Perform instant recovery, writing redo buffer and etc., V$PROCESS
(i) PMON - Doing recover operation when server and dispatcher process terminates abnormally.
(ii) SMON - Doing the recover operation during the instance startup issue, File-Read, tablespace offline errors. Cleaning up unused temporary segments.
(iii) Database Writer Process (DBWn) - Writes content of the database buffer to datafiles. It can allow to create DBW1 to DBW9.
(iv) Log Writer Process (LGWR) - Manages the redo log buffer. Every commit system change number (SCN) will create and make an entry into redo log file.
(II) Dispatcher Process - Similar work of Server process.
(III) Server Process - Work based on Client Request. (E.g., parse sql queries, shared pool, buffer cache, explain and execution plan)
(i) Dedicated Server Process - Take care of the connection between client and server process for the certain duration.
(ii) Shared Server Process - Take care of the connection between client and dispatcher process for the certain duration.
(IV) Slave Process - Addition task of bacground and Server Process.
Memory Structures:
1. Software code areas - Storing software code of oracle.
2. System global area (SGA) - Shared by all oracle server and backaground process. (E.g. Cache data block and shared sql areas). It is an important storage structure.
3. Program global area (PGA) - Stored data and control information. Each server and background process to each PGA.
4. User Global Area (UGA) - Allocated in the PGA.
SQL Work Areas - SQL areas allocated to support memory to process bit complex sql queries.
Database Buffer Cache - Holds the copies of data block read from datafiles.
The LRU Algorithm and Full Table Scans - During full table scans the table data read from the data files and puts them into the LRU to do the quick progression.
Redo Log Buffer - DML and DDL entried would be recorded into redo log buffer.
Shared Pool - It contains library, dictionary and result cache. Also, it holds parallel execution messages and control structures.
Library Cache - It holds/handles sql areas, private sql areas, plsql codes, control structures and locks.
Process:
1. Client processes - To run the application or Oracle tool code (e.g. Sqlplus, toad, sqldeveloper).
2. Oracle processes - To run the Oracle (sql and plsql) Code.
(I) Background Process - To cleaning up, Perform instant recovery, writing redo buffer and etc., V$PROCESS
(i) PMON - Doing recover operation when server and dispatcher process terminates abnormally.
(ii) SMON - Doing the recover operation during the instance startup issue, File-Read, tablespace offline errors. Cleaning up unused temporary segments.
(iii) Database Writer Process (DBWn) - Writes content of the database buffer to datafiles. It can allow to create DBW1 to DBW9.
(iv) Log Writer Process (LGWR) - Manages the redo log buffer. Every commit system change number (SCN) will create and make an entry into redo log file.
(II) Dispatcher Process - Similar work of Server process.
(III) Server Process - Work based on Client Request. (E.g., parse sql queries, shared pool, buffer cache, explain and execution plan)
(i) Dedicated Server Process - Take care of the connection between client and server process for the certain duration.
(ii) Shared Server Process - Take care of the connection between client and dispatcher process for the certain duration.
(IV) Slave Process - Addition task of bacground and Server Process.
Memory Structures:
1. Software code areas - Storing software code of oracle.
2. System global area (SGA) - Shared by all oracle server and backaground process. (E.g. Cache data block and shared sql areas). It is an important storage structure.
3. Program global area (PGA) - Stored data and control information. Each server and background process to each PGA.
4. User Global Area (UGA) - Allocated in the PGA.
SQL Work Areas - SQL areas allocated to support memory to process bit complex sql queries.
Database Buffer Cache - Holds the copies of data block read from datafiles.
The LRU Algorithm and Full Table Scans - During full table scans the table data read from the data files and puts them into the LRU to do the quick progression.
Redo Log Buffer - DML and DDL entried would be recorded into redo log buffer.
Shared Pool - It contains library, dictionary and result cache. Also, it holds parallel execution messages and control structures.
Library Cache - It holds/handles sql areas, private sql areas, plsql codes, control structures and locks.
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