Partitioning Introduction 111101040823 Phpapp01

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Oracle Partitioning -- A Primer


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Partitioning

Partitioning is the ability of the database to take verylarge tables or indexes and

physically break them into

smaller

manageable pieces.


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Partitioned VSNon Partitioned Table


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Partitions - Benefits

Large Table

Difficult to Manage

Partition

Divide and Conquer

Easier to Manage

Improve Performance

Composite Partition

Better Performance

More flexibility to matchbusiness needs

JAN FEB

USA

EUROPE

ORDERS

Transparent to applications

ORDERS

JAN FEB

ORDERS


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Partitioning - Benefits

Faster

Queries will access only those relevantpartitions

Cheaper

An entire partition can be exported

Exported partition can be deleted fromdatabase

Flexible

Partition Maintenance is simpler when

compared to a large un-partitioned table Partition backup/restoration is easier


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When To Partition - Table

Here are some suggestions for when to partition a table:

Tables greater than 2 GBshould always be considered ascandidates for partitioning.

Tables containing historical data, in which new data isadded into the newest partition.

A typical example is a historical tablewhere only thecurrent month's data is updatable and the other 11

months are read only. When the contents of a table need to be distributed across

different types of storage devices.


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Partition Strategies



Partition Type .. (Examples)



Range Partitioned Tables

Data distribution is based on range of values

Data distribution is continuous

Best performance when data distribution is even onthe partition key.

Knowledge of data is critical before choosing this

Definition

Date as partitioning keyJan 2011, Feb 2011, Mar 2011 so on..

Department code as partitioning keyValues 30

Example



DDL Example

CREATE TABLE DEPT (

DEPTNO NUMBER (2),

DEPT_NAME VARCHAR2 (30))

PARTITION BY RANGE (DEPTNO)(

PARTITION D1 VALUES LESS THAN (10)TABLESPACE DEPT1,

PARTITION D2 VALUES LESS THAN (20)TABLESPACE DEPT2,

PARTITION D1 VALUES LESS THAN (MAXVALUE)TABLESPACEDEPT3

)



Range Partition (Multi column)

Defined on two or morecolumns of the table

Multi Column RangePartition

Enhances Query performanceif searched on partition key

Improves the Manageability ofpartitionsAdvantages



When to use Range Partition

Very largetables beingscanned on a

range predicatelike Order-Date

Need to maintainrolling window of

data

Very less timeforadministrativeoperations like

backup on largetables



Hash Partitioning

Partitio

n

Key

Specify thenumber ofpartitions

AlwaysDefine

2n

Partitions

Oracledatabaseinserts

rowsbased onhash valueof partition

key

Storage

Specifystorage forthe entire

table andthetablespacefor

partitions



Hash Partition Example

Hash-partitioned table that splits the table into four parts based onthe hash of the partition key, acct_no.

CREATE TABLE CUST_SALES_HASH (

ACCT_NO NUMBER (5),

CUST_NAME CHAR (30))

PARTITION BY HASH (ACCT_NO) PARTITIONS4

STORE IN (USERS1, USERS2, USERS3, USERS4);



When to use Hash Partition

ImproveManageability/availability of

Large tables

Avoid data skew inpartitions

Maximize I/0 throughput



List Partitioning

Segmenting data with a list of values

Flexible means of partitioning where data is better understood

Similar to Range Partitioning, but without any max valueDefinition

CREATE TABLE DEPT_PART (DEPTNO NUMBER (2),DNAME VARCHAR2 (14),LOC

VARCHAR2 (13))

PARTITION BY LIST (DNAME)

(PARTITION D1_EAST VALUES (NEW YORK),

PARTITION D2_WEST VALUES (SAN FRANCISCO, LOS ANGELES),

PARTITION D3_SOUTH VALUES (ATLANTA,DALLAS,HOUSTON),

PARTITION D4_NORTH VALUES (CHICAGO,DETROIT));

Example


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Range ,List , Hash Partitions


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Composite Partitioning

Data isPartitionedalong two

dimensions

A distinct valuepair for the two

dimensionsuniquely

determines thetarget partition

CompositePartitioning is

complementaryto multi

column rangepartition


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Composite Partitioning Strategies

New 11g Strategy Use Case

List Range Geography Time

Range - Range Ship Date Order Date

List - Hash Geography OrderID

List - List Geography Product


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Range List Partitioning


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Composite PartitioningRange - Range

Jan 2006

... ...

Feb 2006 Mar 2006 Jan 2007

... ...

... ...

...

...

...

...

Jan2006

Feb2006

May

2006

Mar 2006

All records withorder_date inMarch 2006ANDship_date in May2006

May

2006

ship_date

order_date

Table SALESRANGE(order_date)-RANGE(ship_date)


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Partitioning Introduction 111101040823 Phpapp01

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