Oracle DB tuning-2.ppt

7/29/2019 Oracle DB tuning-2.ppt

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Advanced Oracle DB tuning

Performance can be defined in verydifferent ways (OLTP versus DSS)

Specific goals and targets must be set =>clear recognition of success

Factors include response time andthroughput

Oracle specific tuning


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Response time

Sum of service time + wait time

Processing strategy has key effect onresponse time

Eg: Sequential processing

In a queue, wait time for a job = sum ofservice time of all previous jobs

If queue gets longer parallel processingrequired


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response time in Sequential andParallel processing

time

jobs

Wait time

Service time

jobs


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System Throughput

Amount of work completed in a given time Reduced service time = increased throughput

Increase in resources = reduced response time

Under load, contention increases Service may remain the same

But queues get longer

In practice, wait time raises exponentially

O/S scheduler

DB dispatcherWait time

contention


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Critical resources

CPU, memory, I/O capacity, network broadband

Capacity (how many?)

Demand (how many?)

Wait time (how long?) Consumption (how long?)

Software issue as much as hardware issue

Quality of design / programming

Prioritise jobs Performance loss

demand


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Performance adjustments

Reduce consumpt ion (use fewerresources & reduce I/O per transac.)

Demand (reschedule / redistribute work) Capacity (increase / relocate res. eg:

move to parallel proc, increase mem.)


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Problems for DBAs

Many performance parameters are set at designstage => limited scope to adjust

Important targets set at outset => bottlenecks

can be identified Administer trade-offs More $$$

Else reschedule to limit contention

Properly manage user expectations Eg DB versus network problems

Never sacrifice ability to recover data!


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Performance tuning

Always better pro-active =>DBA indevelopment team

On-going tasks minimised by good planning

Service time marginal improvements only

Eg SOCRATE case study

Oracle prioritised tuning steps forapplication dev.


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Oracle tuning methodology

Tune business rules Tune data design Tune application design

Tune logical structure Tune database operations Tune access paths Tune memory allocation

Tune I/O and physical structure Tune resource contention Tune platform


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Business rules

Normally other direction, but sometime businessrule changed for better perf.

Also, IT deployment strategy

Distributed Centralised

Stick to high level analysis of req. => morefreedom (!?)

Cheque printing versus direct deposit Threshold value for automatic approuval

More flexibility in design


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Data Design

Structure for data consistency ANDperformance

Denormalisation

FAReports

Summary values

Data hot spot


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Application Design

In view of DB

In view of Oracle

Data entry acceleration+ Refer to business rules and notes on

critical db operations


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Logical DB structure

Mostly indexing

Also locking strategy


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DB operations

Post relational DBs eg: oracle

Extended SQL functions

New DB functions See Oracle stats on query execution

Also pl/sql server side programming better

than application code Query optimiser may provide clues

Eg: Temporary index on non key attribute


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Memory allocation

Dynamic process in Oracle

Shared pool

Parameters can be set manually Make sure to keep decent SGA

See notes on DB creation


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I/O and physical design

Use multiple disks + parallel controllers

Optimise block size (see notes on DBcreation)

Use extents large enough for indexes

Avoid use of pctincrease in OLTP tables

Use raw device


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Resource contention

Block contention

Shared pool contention

Lock contention All these can be diagnosed with Oracle

stats


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Platform

Need to talk to specialist

Eg: oracle staff

Different for different OS

Cache size

Paging strategies etc


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Application

Always start with specific objectives elsenever achieve anything!

Max response times for inquiry

maximum processing time for document

Picking list

Invoice

Month end Goals may conflict, DBA arbitrates


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Create repeatable tests

SQL statements

New versus old in SQL +

SQL Trace enabled

Trial and error in a trial environment

Use multiple scenarios to test effect ofeach change

Also test in combination

Test for scalability (growth)


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Keep records and automate testing

Write recording into your scripts (table)

Run scripts on a timer

Measure against objectives and past perf. Stop when goals achieved


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Oracle diagnostic tool

Explain plan

Oracle trace

Can be run in combination to compareactuals to estimates


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Oracle Enterprise Manager

Common interface for all utilities

Diagnosis + implementation of changes

See table 17.4


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Benchmarking

Use in product selection Vendor bias?

Env tuned for test only

Not repeatable without access to unlimited resources

Hidden cost of table maintenance outside the test. Cited by every DB vendor on this planet

Creation of the TPC (Transaction ProcessingPerformance Council) TPC C: order entry benchmark

TPC H and TCP R: decision support benchmark

TPC A: web transaction benchmark

Open source DB benchmark

Oracle DB tuning-2.ppt

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