Database Tuning in

- Philip K. Kuruvilla

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Login

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The World Wide Wait

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Looks Familiar ?

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Agenda

• Why tune databases• Scope for tuning• Parameters• Design• Monitor and Analyze• Trivia

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Why is it so critical?

Web Server

Database

The Database lies at the root of an e-commerce application !

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Scope for Tuning

• System level• Operating System, Hardware

• Database level• Temporary space, Rollback segments

• Application level• Query Tuning, Design

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Tuning Parameters

• Throughput and Response Time• Throughput: Ratio of total data read to

total time spent in servicing the request• Response Time: Difference between

time at which a request is completed and response is received

• Type of Application• OLTP (requires better throughput)• Batch processing (requires shorter

response time)

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Design

• Normalization• Not always a good idea to Normalize

• Better to have a single table here

Banner ID Professor

B0000001 G. Sullivan

B0000002 T. Trappenberg

B0000003 S. Marche

B0000004 A. Uteck

Banner ID Course

B0000001 ECMM6000

B0000002 ECMM6010

B0000003 ECMM6020

B0000004 ECMM6030

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Application Design

• Simple and efficient queries• Minimise the number of query blocks

SELECT * FROM ALL_STUDENTS A WHERE A.NAME IN

(SELECT GS.NAME FROM GRAD_STUDENTS GS)

SELECT * FROM ALL_STUDENTS A, GRAD_STUDENTS GS WHERE A.NAME = GS.NAME=

• Return efficient batch sizes• Use Stored Procedures/ Functions/ Triggers•Startup costs are high. Running costs are low

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Indexes• What are they?

• Defined on a column• Avoid full table scans

• How do they work• When do they NOT work !• Trade off between insert/update

and select• Primary keys are automatically

indexed

rowID (hidden )

Banner ID

Name Age Tel

1 B001 Chris 20 23232

2 B005 Bates 21 23232

3 B003 Hugh 29 23902

4 B010 Mark 28 23902

5 B008 Martin 33 23920

6 B002 Jones 22 32902

Banner ID Row ID

B001 1

B002 6

B003 3

B005 2

B008 5

B010 4

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Monitoring

• Plan table• Shows how an SQL query is executed• Shows use of indexes, effect of

Optimizers• Gives a “cost factor” for a query

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Explain Plan table

LNAME

FNAME

CUST_ID

CUSTOMER

TOTAL

CUST_ID

ORDER_ID

PRODUCT_ORDER

QTY

PRODUCT ID

ORDER_ID

ORDER_DETAIL

Indexed ColumnNon Indexed Column

SELECT POD.PROD_ID, POD.QTY FROM CUSTOMER C, PRODUCT_ORDER PO, PRODUCT_ORDER_DETAIL PODWHERE C.CUST_ID = 2 AND PO.CUST_ID = C.CUST_ID AND PO.ORDER_ID = POD.ORDER_ID

SELECT POD.PROD_ID,

POD.QTY

FROM CUSTOMER C,

PRODUCT_ORDER PO,

PRODUCT_ORDER_DETAIL POD

WHERE PO.CUST_ID = 2

AND PO.CUST_ID = C.CUST_ID

AND PO.ORDER_ID = POD.ORDER_ID

SELECT POD.PROD_ID,

POD.QTY

FROM PRODUCT_ORDER PO,

ORDER_DETAIL POD

WHERE PO.CUST_ID = 2

AND PO.ORDER_ID = POD.ORDER_ID

SELECT STATEMENT Optimizer=CHOOSE (Cost=3 Card=1 Bytes=51)

NESTED LOOPS (Cost=3 Card=1 Bytes=51)

NESTED LOOPS (Cost=2 Card=1 Bytes=39)

INDEX (UNIQUE SCAN) OF SYS_C003983 (UNIQUE)

TABLE ACCESS (FULL) OF PRODUCT_ORDER (Cost=1 Card=1 Bytes=13)

TABLE ACCESS (FULL) OF PRODUCT_ORDER_DETAIL (Cost=1 Card=7 Bytes=84)

SELECT STATEMENT Optimizer=CHOOSE (Cost=3 Card=1 Bytes=38)

NESTED LOOPS (Cost=3 Card=1 Bytes=38)

NESTED LOOPS (Cost=2 Card=1 Bytes=26)

INDEX (UNIQUE SCAN) OF SYS_C003983 (UNIQUE)

TABLE ACCESS (FULL) OF PRODUCT_ORDER (Cost=1 Card=1 Bytes=13)

TABLE ACCESS (FULL) OF PRODUCT_ORDER_DETAIL (Cost=1 Card=7 Bytes=84)

SELECT STATEMENT Optimizer=CHOOSE (Cost=2

Card=1 Bytes=25)

NESTED LOOPS (Cost=2 Card=1 Bytes=25)

TABLE ACCESS (FULL) OF PRODUCT_ORDER (

Cost=1 Card=1 Bytes=13)

TABLE ACCESS (FULL) OF PRODUCT_ORDER_DETAIL (Cost=1 Card=7 Bytes=84)

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Advanced• Trace functionality

• Real time data• Can identify deadlocks, excessive waits

• Optimizers within Oracle • Rule Based Optimizer (RBO)

• Uses Pre–determined rules• Independent of data

• Cost Based Optimizer (CBO)• Optimizes based on table/ index information gathered• Requires that database is analyzed frequently• Default in Oracle

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Summary

• Tuning is a series of trade offs• Always better to tune during the

design phase than after implementation

• Sometimes it’s plain common sense !

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Trivia• Oracle has been the leading database

manufacturer for the last 5 years. (source: IDC, 2003)• Oracle: 39.4%, DB2: 33.6%, SQL Server: 11.1%

• Broad coverage of OS (Windows, Unix & Linux)• “Unbreakable Campaign”

• Advertising campaign in Late 2001. Declared that Oracle 9i was “unbreakable”

• Open challenge to hackers

• Windows “Long Horn”. Will feature a new File system “WinFS” which will store files using “database technologies” (source: Microsoft)

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References• Metalink – http://metalink.oracle.com• Oracle Performance Tuning - Richard J.Niemiec, - Oracle

Press • Database Design Fundamentals – Naphtali Rishe,1988 –

Prentice Hall• “Oracle Market share”

http://www.oracle.com/ip/index.html?database1.html• “Unbreakable system”

http://www.oracle.com/oramag/oracle/02-mar/index.html?o22break.html

• “Microsoft LongHorn” http://msdn.microsoft.com/Longhorn/understanding/pillars/WinFS/default.aspx