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Introduction To IBM Universal Database For Linux, UNIX And Windows

1. Database Objects

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Agenda

Overview of database objects

Overview of storage objects

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Database Objects

Instances

Databases

Schemas

System catalog tables and views

Tables

Indexes

Views

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DB2 Object Hierarchy

Database 1 Database 2

DBM configuration fileInstance 1

Catalog

Log

DB configuration file

Catalog

Log

DB config. file

Table1

Index1

BLOBs

Table2 Table3

View1

View2

View3

Index1

Index2

Table2

View1

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Instance, Database, Table Spaces And Tables

Databases are created in DB2 instances

Table spaces are a logical layer created within a database

Tables are created within table spaces

Table 2

Database Manager

Instance

Database1

Tablespace A

Database2

Table 1 Table 3

Tablespace B

Table 4

Tablespace ATable 1 Table 2

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DB2 Instance

Also known as database manager (DBM)

DB2 code that manages data, controls what can be done to the data

Manages system resources assigned to it

An instance has its own databases (which other instances cannot access)

Separate security from other instances on the same machine

All its databases share the same system directories

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DB2 Instance Administration

DB2 instance creation / migration / updating done by user root on Linux/UNIX (Administrator on Windows)

Programs located in sub-directory instance (Linux, UNIX) respectively bin (Windows)

– Example Linux V8.1: /opt/IBM/db2/V8.1/instance

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DB2 Instance Administration (Cont’d)

Overview of some important DB2 Instance administration tools:

– db2icrt (creates DB2 instance)

– db2ilist (lists DB2 instances on server)

– db2iupdt (updates DB2 instances – e.g. after Fix Pack installation)

– db2imigr (migrates DB2 instances – e.g. from V7.2 to V8.1)

– db2idrop (drops DB2 instances)

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DB2 Instance Commands

To start the DB2 Instance / Database Manager, enter:

– db2start

To stop the DB2 Instance / Database Manager, enter:

– db2stop (Command will fail if databases are still active)

To force off all active applications before stopping DB2 Instance, use:

– db2stop force

Emergency Stop of DB2 Instance / Database Manager

– db2_kill (Crash Recovery necessary prior accessing database again)

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CREATE DATABASE Syntax

CREATE DATABASEDB . . .

Create Database Options

database-name

USING CODESET TERRITORYcodeset territory

CATALOG TABLESPACE | tblspace-defn | USER TABLESPACE | tblspace-defn |

Create Database options:

ON ALIASpathdrive

database-alias

DFT_EXTENT_SZ dft-extentsizeCOLLATE USING SYSTEM

IDENTITY

tblspace-defn:,

EXTENTSIZE PREFETCHSIZEnumber-of-pages number-of-pages

WITHTEMPORARY TABLESPACE | tblspace-defn |

"comment-string"

TRANSFERRATEOVERHEAD number-of-milliseconds number-of-milliseconds

| MANAGED BYSYSTEM USING

DATABASE USING FILEDEVICE

'container-string'

'container-string' number-of-pages

(

(

)

),

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Tasks Completed By DB2 During CREATE DB

1. Creates database

2. Creates SYSCATSPACE, TEMPSPACE1 and USERSPACE1 table spaces

3. Creates system catalog tables and recovery log

4. Catalogs database in local database directory and system database directory

5. Assigns codeset, territory, and collating sequence

6. Creates SYSCAT, SYSFUN, SYSIBM, SYSSTAT schemata

7. Binds previously defined database manager bind files to the database (db2ubind.lst)

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Tasks Completed By DB2 During CREATE DB

8. Grants privileges: DBADM authority with CONNECT, CREATETAB, BINDADD,

IMPLICIT_SCHEMA, CREATE_NOT_FENCED and LOAD privileges to database creator

SELECT privilege on system catalog tables and views to PUBLIC BIND and EXECUTE privileges to PUBLIC for each successfully

bound utility CREATETAB, BINDADD, IMPLICIT_SCHEMA, and CONNECT

privileges to PUBLIC Use privilege on USERSPACE1 table space to PUBLIC

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DB2 Directory Structure

SQLT0000.0

SQLT0001.0

SQLT0002.0

Drive / Directory

DB2 Instance NameDB2 Instance Name

NODE0000

SQL0001

SQLOGDIR

The drive or directory specified on the CREATE DATABASE command

The name of the DB2 instance owner

The partition number of the database, 0 for a non-partitioned database

The database ID, starts at 1, increases for all subsequent databases

The catalog table space, SYSCATSPACE

The temporary table space, TEMPSPACE1

The user table space, USERSPACE1

The default log directory for the database

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System Catalog Tables

Each database includes a set of system catalog tables, which describe the logical and physical structure of the data

DB2 creates and maintains an extensive set of system catalog tables for each database

You cannot explicitly create or drop them, but you can query and view their contents using the catalog views

SYSCAT

SYSSTAT

views

SYSIBM.SYSCOLUMNSSYSIBM.SYSTABLES

......

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Tables

A table is an unordered set of data records. It consists of columns and rows that are generally known as records

Tables can either be permanent (base) tables, temporary (declared) tables, or temporary (derived) tables

All database and table data is assigned to table spaces

The data in the table is logically related, and relationships can be defined between tables

Data can be viewed and manipulated based on mathematical principles and operations called relations

create table artists(artno smallint not null, name varchar(50) with default'abc', classification char(1) not null, bio clob(100K) logged, picture blob( 10M) not logged compact) in dms01 index in dms02 long in dms03;

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Indexes

An index is a physical object that is associated with a single table

Indexes are used to force uniqueness in a table (that is, to make sure that there are no duplicate values) and to improve performance when retrieving information

An index is a set of keys, each pointing to rows in a table. The index allows more efficient access to rows in a table by creating a direct path to the data through pointers

– The SQL optimizer automaticallychooses the most efficient way to access data in tables

create unique index itemno on albums (itemno)

create unique index empidx on employee (empno) include (lastname, firstname)

create index item on stock (itemno) cluster

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Views

A view is an efficient way of representing data without needing to maintain it

A view is not an actual table and requires no permanent storage but to the user, a view just looks like a table

A view can include all or some of the columns or rows contained in the tables on which it is based

– A view can be used to restrict which rows and columns can be viewed or updated by certain users

CONNECT TO TESTDBCREATE VIEW EMPSALARY AS SELECT EMPNO, EMPNAME, SALARY FROM PAYROLL, PERSONNEL WHERE EMPNO=EMPNUMB AND SALARY > 30000.00

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Storage Objects

Table space

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Table Spaces

Database managed storage (DMS) versus system managed storage (SMS)

Default database configuration

Create Tablespace syntax

Getting info about table spaces and containers

Alter Tablespace syntax

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SMS Versus DMS

A table space can be either system managed space (SMS), or database managed space (DMS)

For an SMS table space, each container is a directory in the file space of the operating system, and the operating system's file manager controls the storage space

For a DMS table space, each container is either a fixed size pre-allocated file, or a physical device such as a disk, and the database manager controls the storage space

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Containers And Table Spaces

A container is an allocation of physical space

File

DirectoryDevice

File Directory Device

SMS

DMS

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SMS Tablespace Summary

Containers are operating system directories

– Can easily increase table space capacity by enlarging underlying operating system file system

Data striped across container by extent

Disk space allocated on demand

– One page at a time (by default)

Data "objects" (i.e.. table data, indexes, LONG VARCHARs, LOBs) located by operating system file name

Tips:

– Associate each container (i.e. directory) with a different file system (otherwise table space capacity limited to that of a single file system)

– Ensure containers have equal capacity (excess in larger containers isn't exploited)

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DMS Tablespace Summary

Containers are either operating system files or raw devices

– Can increase table space capacity via ALTER TABLESPACE command

Data striped across container by extent

Disk space allocated at table space creation

– SMPs (space map pages) keep track of what extents are used and which are free

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Table Placement In DMS

DB2 is able to distribute one table across multiple DMS table spaces

DMS table space with three data types:

– Regular, (user | system) temporary and large (large table spaces can be used for indexes too)

Table Space DATA Table Space INDEX Table Space LARGE

EMPLOYEE DATA EMPLOYEE INDEX LARGE DATA FOR EMPLOYEE TABLE

= Data Portion of Employee

= Index Portion of Employee

= Large Data Portion of Employee

Create table employee <table definition> index in INDEX long in LARGE

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Defining Table Spaces

When defining a table space, you can

– Specify containers and their description

– Specify storage type

– Specify type of data

– Specify extent size

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Writing To Table Space Containers

The extent size is the number PAGESIZE (default 4k) pages that the database will write to a container before skipping to next container (data is written in round-robin manner)

– DFT_EXTENT_SZ defined at database level (default extent size)

– EXTENTSIZE defined at CREATE TABLESPACE command

1page

Extent = 32 Pages(Default)

Container 0

0 2 Container 1

13

Tablespace B

Extent

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Reading From Table Spaces

Prefetching reads in data needed by a query prior to it being referenced by the query, so that the query need not wait for the underlying system to perform I/O operations

PREFETCHSIZE specifies the number of PAGESIZE (default 4k) pages that will be read from the table space when data prefetching is being performed

– PREFETCHSIZE defined at CREATE TABLESPACE command

– Can be altered with the ALTER TABLESPACEcommand

1 page

I/OServer

Synchronous Read

Prefetch Read

Buffer PoolDatabaseEngine

Data accessis faster

DFT_PREFETCH_SZNUM_IOSERVERSSEQDETECT

Prefetch Read

I/OServer

I/OServer

Prefetch Read

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CREATE TABLESPACE Syntax (1/2)

OVERHEAD

24.1

number-of-milliseconds

MANAGED BY SYSTEM | system-containers |DATABASE | database-containers | number-of-pagesEXTENTSIZE

integer KMG

BUFFERPOOL bufferpool-namenumber-of-pages

integer

PREFETCHSIZE

KMG

TRANSFERRATE

0.9

number-of-milliseconds

REGULAR

CREATE

LONG

tablespace-nameTABLESPACEPAGESIZE 4096

PAGESIZE integerK

SYSTEM

USERTEMPORARY

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Creating SMS Table Spaces

UNIX: create tablespace enterprise managed by system using ('/database/firstcontain', '/database/secondcontain', '/database/thirdcontain') prefetchsize 32

Windows: create tablespace enterprise managed by system using ('E:\db\firstcnt', 'F:\db\sndcnt', 'G:\database\thirdcnt') prefetchsize 32

Indicates SMS Table Space

Indicates SMS Table Space

Table Space Container Definitions

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Creating DMS Table Spaces

create tablespace humanres managed by database using (device '/dev/data1' 1024, device '/dev/rdata2' 1024) extentsize 8 prefetchsize 16

UNIX:

create long tablespace longtbs managed by database using (file '/data/longtbs/cont.001' 500M, file '/data/longtbs/cont.002' 500M) extentsize 8 prefetchsize 16

Windows:

Indicates DMS Table Space

Table Space Container Definitions

Table Space Storage Type

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Example – DB2 List Tablespaces Show Detail

db2 list tablespaces show detail

Tablespaces for Current Database

Tablespace ID = 0 Name = SYSCATSPACE Type = System managed space Contents = Any data State = 0x0000 Detailed explanation: Normal Total pages = 1729 Useable pages = 1729 Used pages = 1729 Free pages = Not applicable High water mark (pages) = Not applicable Page size (bytes) = 4096 Extent size (pages) = 32 Prefetch size (pages) = 32 Number of containers = 1

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Example – DB2 List Tablespaces Show Detail

Tablespace ID = 5Name = LONGTBSType = Database managed spaceContents = Long data onlyState = 0x0000 Detailed explanation: NormalTotal pages = 1024Useable pages = 992Used pages = 96Free pages = 896High water mark (pages) = 96Page size (bytes) = 4096Extent size (pages) = 32Prefetch size (pages) = 32Number of containers = 1

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Changing The Size Of A Table Space

The size of a DMS table space can be changed (increased and decreased) online. The table space is still accessible to users

– A SMS table space size is altered through changing of underlying file system

– Data will be rebalanced across containers automatically if needed

Rebalance done asynchronously after the following ALTER TABLESPACE options:

– ADD container (forward rebalancing)

– DROP container (reverse rebalancing)

To avoid rebalancing choose the following ALTER TABLESPACE options:

– RESIZE / EXTEND / REDUCE container

– BEGIN NEW STRIPE SET