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DB Tuning
Ch 14. Parallel Processing
Ch 15. Performance of DML
Ch 16. Analytic Function
Jaeseok Myung
Intelligent Database Systems Lab
School of Computer Science & Engineering
Seoul National University, Seoul, Korea
Center for E-Business Technology
Seoul National University
Seoul, Korea
Parallel Processing


Goal

Utilization of System Resource

Reduction of Response Time
–
Multi-Processes
–
Response Time = CPU Time + Wait Time
Architecture


Query Coordinator
–
Syntactic Analyzing
–
Assign small jobs to slaves
–
Generate final result
Slave Process
–
Do works
–
Send results
Copyright 2008 by CEBT
DB Tuning - 2
How to PP
 Parameters in Oracle

Parallel_min_server
–

Determine initial minimum, Default : 0
Parallel_max_server
–
Determine initial maximum, Default : 5, Max : 255
 Two ways of using PP functionality

Insert a hint into a query
–

SELECT /*+ PARALLEL(A, 2) */ user, sum(amount)
FROM sales_history GROUP BY user;
Alter the degree of table
–
ALTER TABLE sales_history PARALLEL 2;
Copyright 2008 by CEBT
DB Tuning - 3
Execution Plans of PP
Copyright 2008 by CEBT
DB Tuning - 4
Execution Plans of PP
 Parallel_from_serial, Parallel_to_serial, Parallel_to_parallel
 Parallel_combined_with_parent, Parallel_combined_with_child
Copyright 2008 by CEBT
DB Tuning - 5
DB Tuning
Ch 14. Parallel Processing
Ch 15. Performance of DML
Ch 16. Analytic Function
Jaeseok Myung
Intelligent Database Systems Lab
School of Computer Science & Engineering
Seoul National University, Seoul, Korea
Center for E-Business Technology
Seoul National University
Seoul, Korea
Issues on DML Processing
 Excessive Requests for Resources

Rollback Segment

Redo Log

Disk IO
 Excessive Indices

Overhead for index management
 A Misguided Execution Plan

We can put ‘where clause’ into the DML
Copyright 2008 by CEBT
DB Tuning - 7
Insert (1)
 Conventional Insert

INSERT INTO TAB1 VALUES (COL1, COL2);

Index, Disk IO Tunings can be applied
 A special ‘insert’ including ‘select’ has more options

INSERT INTO TAB1
SELECT COL1, COL2 FROM TAB2 WHERE COL3 > 100;

Direct Loading

Parallel Direct Loading

Nologging
Copyright 2008 by CEBT
DB Tuning - 8
Direct Loading

INSERT INTO TAB1 ~;

INSERT INTO /*+ APPEND */ TAB1 ~;
Copyright 2008 by CEBT
DB Tuning - 9
Insert (2)
 Parallel Direct Loading

Direct Loading + Parallel Functionality

ALTER SESSION ENABLE PARALLEL DML;

INSERT /*+ PARALLEL (A, 4) */ INTO TAB1
 Nologging

Only be allowed with Direct Loading or Parallel Direct Loading

ALTER TABLE TAB1 NOLOGGING;

We may need backup
Copyright 2008 by CEBT
DB Tuning - 10
Delete & Update (1)
 Resources

Need more rollback segment than insert operation

More RedoLog, More Disk IO
Copyright 2008 by CEBT
DB Tuning - 11
Delete & Update (2)
 Checkpoint

Index Counts

Execution Plan – Where Clause
 Parallel Hint

DELETE /*+ PARALLEL (A, 4) */ ~;

UPDATE /*+ PARALLEL (A, 4) */ ~;
 Alternatives

Use ‘Insert’ instead of ‘Delete’ if we have too much data

Less RedoLog, Less Rollback Segment
Copyright 2008 by CEBT
DB Tuning - 12
DB Tuning
Ch 14. Parallel Processing
Ch 15. Performance of DML
Ch 16. Analytic Function
Jaeseok Myung
Intelligent Database Systems Lab
School of Computer Science & Engineering
Seoul National University, Seoul, Korea
Center for E-Business Technology
Seoul National University
Seoul, Korea
Analytic Function

Keep SQL queries to be simple

Use less GROUP BY

SELECT deptno, name, sal,
COUNT(sal) OVER (PARTITION BY deptno ORDER BY sal)
FROM employee;

AVG, COUNT, MIN, MAX, …

Tune indices carefully
Copyright 2008 by CEBT
DB Tuning - 14
Conclusion
 How much helpful? – It’s not a critical section

Ch 14. Parallel Processing

Ch 15. Performance of DML

Ch 16. Analytic Function
 But, Interesting
 Thank you
Copyright 2008 by CEBT
DB Tuning - 15