DB2 UDB FOR Z/OS

Overview

DB2-DM-1

An Introduction

Data Management in DB2

DB2 Data Objects

Storage Group

Databases

Table spaces

Indexes

TABLES

SYNONYM

VIEW

Buffer pools

DB2 CATALOG

STORAGE GROUP

A storage group (stogroup) is a set of DASD volumes from which DB2 can assign space for tables and indexes.

All volumes of a storage group must be the same device type.

A storage group is used to:

Have DB2, rather than the user, allocate the VSAM data sets for table spaces and indexes.

Simplify the management of DB2 data sets.

STOGROUP 1

VOL1

VOL3 VOL2

STOGROUP 2

VOL4

VOL5

STOGROUP 3

VOL3

DB2-DM-2

DB2 Tablespaces

Physical Representation

Logical Representation

DB2 Transformation

TABLESPACE

DATABASE

TABLESPACE

T

T

T

T T

TABLESPACE

T

T

T

T T

VOL1

VOL3

VOL2

TABLESPACE

A table space is one or more data sets in which one or more tables are stored.

A table space may consist of from 1 to 64 VSAM data sets.

The data sets may contain up to 64 gigabytes of data altogether.

Table space is the unit of recovery in DB2.

There are three types of table spaces:

Simple

Partitioned

Segmented

DATABASE

TABLESPACE

T

T

T

T T

TABLESPACE

T

T

T

T T

vsam1

vsam2

vsam

Simple TABLESPACE

Simple

Has one VSAM data set for every two gigabytes.

Contains rows from one or more tables on a page.

Can hold one or more than one table in table space

Scanning rows in one table requires Scanning the entire table space.

Updating row in one table causes the entire table space to be locked

VSAM 2 VSAM1

Partition TABLESPACE

Partitioned

Table space is divided into partition and each partition is stored in one VSAM/ESDS.

Holds only one table and each partition stores a part of the table. One table split across multiple areas of a table space.

Table physically separated into key range partitions

Large tables can be split across multiple DASD Volumes

A-G

H-P

Q-Z

Segmented TABLESPACE

Segmented Can hold more than one

table

Locking at Table level.

If table scan is necessary , only segments assigned to the table will be scanned.

Segment contains same number of pages which is multiple of 4 .

Segment is made up of 4 to 64 consecutive pages.

Contains rows from only one table in a segment.

More efficient than a simple table space.

DB2-DM-3

Pages

• A Page is either 4K or 32K

A Page is the unit of I/O

A Page can contain a maximum of 127 data records.

A data record does not span pages

HEADER

FOOTER

PAGE

SPACE

Data Records

USING A PAGE OF DATA

Table spaces are divided into equal-sized units called pages.

A page can be either 4K or 32K in size, and is always composed of 4K VSAM Control Intervals (CI).

Rows of data are stored on a page.

Up to 255 rows of data are allowed on a single page

A page is used as follows:

A program must use a row of data.

If the page containing the row is already in the buffer pool, no I/O is done.

If the page is not in the buffer pool, an I/O is done to transfer the page from DASD to the buffer pool. The page is the I/O unit for DB2.

Once the page containing the desired row is in the buffer pool, data is transferred from the row to the program, column by column.

Page 01

Page 02

Page nn

Program

I/O Area

Buffer Pool

0006 0029

Smith Jones

490112 550911

Empno Name Birthdate

INDEXES

Indexes

An index is an ordered set of pointers to the data in a DB2 table, stored separately from the table.

Each index is based on the values of data in one or more columns of a table.

You can use an index to:

Optimize data access.

Guarantee uniqueness.

Empno Lastname Jobcode DeptnoPage-Row

120 O'Connell 58 A00060 Stern 55 D11090 Henderson 55 D11

123

1

130 Quintana 55 C01030 Kwan 60 C01190 Walker 53 E11

123

2

290 Parker 42 E1113

Index on Empno

030 2-2060 1-2090 1-3120 1-1130 2-1190 2-3290 3-1

Index Data

DB2 TABLE

All data in a DB2 data base is stored in tables.

A table is a collection of rows, all having the same columns.

Rows are similar to record occurrences in a file.

Columns are similar to fields within a record.

Rows

Table

C o l u m n s

Field 1 Field 2Field 1 Field 2

Field 1 Field 2 Field 3 Field 4

Record

Sequential File

VIEWS

A view is a logical (or “virtual”) table that is derived from one or more tables.

It does not physically exist.

A view can:

Be made up of selected columns from a table.

Be made up of selected rows from a table.

Include data from more than one table.

• Data Security • Data Independence

View

Base TableA B C D E

1

2

3

4

5

A B D

1

2

5

SYNONYMS

Another name for a table or view

Can be used only by its creator

Can not be qualified

Only for local table or view

Synonyms

A synonym is a different name by which a table or view is known.

Synonyms can be used to:

Eliminate the need to specify the table AUTHID.

Synonyms are useful in avoiding fully qualifying table names that are frequently used, such as:

Assigned TABLE name: ACCT_TABLE TABLE created by: PLTNM01 Your USERID: STUDENT1

Without a synonym, STUDENT1 can reference the table only as: PLTNM01.ACCT_TABLE

After the creation of a synonym (by STUDENT1):

CREATE SYNONYM ACCOUNT_TABLE FORPLTNM01.ACCT_TABLE

STUDENT1 can reference the table as:

SELECT * FROM ACCOUNT_TABLE

A synonym can only be used by its creator and can only refer to a local table or view.

ALIAS

An alternate name for a table or view

Can be used by anyone . Can be qualified

Can describe local or remote tables

Are not dropped when the described table is dropped.

An alias is similar in usage to a synonym but without most of a synonym's restrictions.

Aliases are useful in assigning customer meaningful names to tables:

Assigned table name: T00101

TABLE created by: ENPIP41

After creation of alias by DBA:

CREATE ALIAS ENPIP41.ACCT_TABLE FOR

ENPIP41.T00101

Anyone can reference the table as

SELECT * FROM ENPIP41.ACCT_TABLE

Aliases are useful for accessing remote tables:

A three part name is used for remote tables:

location.creator.table

CREATE ALIAS ENPIP41.ACCT_TABLE FOR

NEWYORK.ENPIP41.ACCT_TABLE

ALIAS VS VIEW

When To Use An Alias vs. A View

FUNCTION DB2 OBJECT TO USE

Assigning customer meaningful names (local or remote)

Alias

Accessing remote tables Alias

Restricting access to certain columns and/or rows for security

View

Creating a logical view from more than one table (join)

View

Create Data Base Create Table Space Create Table Create Index Insert/Load Row

DB2

Catalog

D B 2

VSAM

VSAM Catalog

VSAM Linear

Data Set

VSAM Linear

Data SetData Base

Table Space

Index Space

Index

Table

Row

Updating DB2 Catalog

DB 2 Objects Hierarchy

STOGROUP

DATABASE

TABLESPACE

TABLE

COLUMN

INDEX

SYNONYM

ALIAS

VIEW

Threads

DB2Call

Attach pgm

CICS PGM

DB2Utility

TSO O/L

PGM

QMF Or

DB2I

TSOBatchpgm

IMS Batchpgm

IMS/DCPGM

Are memory structures used by DB 2 to communicate

with an application program.

Serves as links between DB 2 and application

programs.

Application programs send all requests to DB 2

through threads.

DB 2 communicates the status of each SQL statement

to the application using threads through SQLCA.

Components of DB2 System

Overview

MAJOR COMPONENTS OF DB2

The four major components of DB2 are 

System Services Component

Locking Services Component

Database Services Component

Distributed Data Facility Component

System Services Component, which supports System operation, Operator communication, Logging and similar functions.

 Locking Services Component, which provides the necessary controls for managing concurrent access to data.

Database Services Component, which supports of the definition, retrieval and update of user and system data.

 Distributed Data Facility Component, which provides DB2 database support.

DB2 Components

AlliedAgent

CICSIMSTSO

System service

LoggingRecovery

Acces to TP

VSAM

Media Manager

IRLMInternal

resource Lock

Manager

Locking

DDF

DistributedData

FacilityAccess

To distributed

data

Data

Database Service

OptimizerData manager

Buffer Manager

SYSTEM SERVICES

This system services component handles all system wide tasks.

   Controlling Connections to other MVS Subsystems (CICS, IMS & TSO)

  Handling system startup and shut down and operator Communication.

  Managing the System log

  Gathering system wide statistics performance, auditing and accounting information.

  These are provided by an MVS subsystem called the IMS Resource Lock Manager (IRLM). This IRLM is used to control concurrent access to Db2 data, regardless whether IMS is present in the system or not.

 

LOCKING SERVICES

DATABASE SERVICES

           

SQL Syntax Checking

DATA DICTIONARY

PRECOMPILER

BIND

Buffer Manager

DATA MANAGER

Insertion/Reterival/ Index Maintenance

DBADM RESPONSIBILITIES

    Build and maintain objects within the database.

Grants to other users the privilege to access or change objects within the database.

Perform the binds (prepare application programs to work with DB2)

DBADM is responsible for the running of most DB2 utilities 

SYSADM RESPONSIBILITIES

     Install new releases Grant of privileges Creating system level objects Monitoring System performance

Notes: SYSADM may install or assist in the install of DB2 and fixes.

SYSADM grants privileges (DBADM, CREATETAB, CONNECT Etc).

SYSADM creates the system level objects like Databases, Table spaces etc.

SYSADM monitors DB2’s performance using tools like DB2 PM.

PROGRAMMER RESPONSIBILITIES

Create the test environments for new applications.

•  Prototypes (write and test the SQL before it is used in production).

• Check that SQL statements access the data most efficiently.

•  Physically embed SQL in host language programs.

•  Prepare (precompile and bind) programs for execution.

END-USER RESPONSIBILITIES

Anyone who executes an SQL statement is an end-user.

SQL can be in the applications the end-users run. SQL within the applications may read, add, change or remove data Produce reports after giving necessary input data. Write their own SQL to change data or produce reports.

OPERATOR’S RESPONSIBILITIES

Run the utilities for maintaining the data like: ·        Loading data

·        Backing up the data

·        Restoring the database

·        Importing data into DB2