db2 unit 2

7/27/2019 DB2 UNIT 2

1/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 1 of 33

DB2

TRANSPARENCIES

(Unit 2)

7/27/2019 DB2 UNIT 2

2/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 2 of 33 2

DB2

IBM DATABASE2 (DB2) is IBM's RelationalData Base Product.

Runs under MVS.

DB2 can be accessed through threeenvironments : TSO, CICS, MVS.

Employs TSO for both interactive and batch

processing.

DB2 may be accessed by IMS and CICS

Transaction Managers concurrently.

DB2 provides a language interface through

SQL for data definition, manipulation,

access and authorization operations.

7/27/2019 DB2 UNIT 2

3/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 3 of 33 3

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

4/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 4 of 33 4

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

5/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 5 of 33 5

Benefits of DB2 Ease of use.

Non-procedural. (Specify what data you

want, not how to get it)

DB2 uses Optimizer for selecting the

access path to the required data.

Provides interactive facilities for :

Testing

Debugging Program preparation and execution

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

6/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 6 of 33 6

Benefits of DB2 (Contd..)

Provides full data protection including

data security, data integrity and data

recovery.

Reduces application design and

development efforts.

Provides a language interface.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

7/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 7 of 33 7

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

8/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 8 of 33 8

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

9/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 9 of 33 9

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

10/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 10 of 33 10

Components of DB2

Locking Services : IRLM (IMS Resource

Lock Manager)

DB2 treats data as a shared recourse

Any number of users can access the

same data simultaneously

A concurrency control mechanism is

required to isolate the users from one

another

IRLM provides this mechanism which

is called Locking

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

11/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 11 of 33 11

Components of DB2 (Contd..)

System Services

Controls the overall DB2 executionenvironment

Manages log datasets

Gathers statistics for performance

monitoring

Handles system startup & shutdown.

Controls attachment to other MVS

subsystems such as CICS, TSO etc.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

12/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 12 of 33 12


System Services (Contd..)

Performs commit, rollback,

checkpoint and recovery.

Supports operator communication

and logging functions

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

13/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 13 of 33 13


Database Services

Supports the functions of SQL i.e.definition, access control,

manipulation of user & system data.

Supervises access to the physicaldatabase.

Uses buffering to control the actual

transfer of data between secondary

storage and virtual storage buffers.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

14/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 14 of 33 14

Other DB2 Features

DB2 Subsystem

A copy of DB2 that runs on a CPU

One CPU can have more than one

DB2 subsystems running on it

Information about DB2 subsystem is

maintained in DB2s Directory and

Catalog.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

15/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 15 of 33 15

Other DB2 Features

Directory

Solely for DB2s internal use.

Catalog

It is a set of system tables.

Contains approximately thirty tables.

Contains descriptive information about

DB2 objects.

DB2 users can only query the Catalogtables but not modify them.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

16/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 16 of 33 16

DB2 Features (Contd..)

DB2 Catalog tables for security

__________________________________

Table Name DESCRIPTION

_________________________________________

Records privileges

held by auth-ids

over:

SYSIBM.SYSCOLAUTH Specific columns in

tables and views

SYSIBM.SYSTABAUTH Tables and views.

SYSIBM.SYSDBAUTH Databases.

SYSIBM.SYSPLANAUTH Application plans.

SYSIBM.SYSUSERAUTH The DB2 subsystem.

SYSIBM.SYSTESAUTH Tablespaces, storage

groups and

bufferpools.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

17/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 17 of 33 17

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

18/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 18 of 33 18

DB2 as Perceived by an Individual

User

There will be many users, all operating

on the same data at the same time.Users are protected from one another.

Tables are of two types

Base Tables Views

A base table is a real table that exists

physically.

A View is a virtual table that does not

actually exist in the physical storage but

looks to the user as if it did.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

19/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 19 of 33 19

Database Services

Supports the definition, retrieval and

update of user & system data.

Subcomponents are:

Precompiler (PRECOM)

Bind (BIND)

Runtime Supervisor (RS)

Data Manager (DM)

Buffer Manager (BM)

These together allow: Preparation of application programs

for execution.

Subsequent execution of these

programs

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

20/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 20 of 33 20

Database Services (Contd..)

Precompiler

Preprocessor for the host language

Function

Analyze a host language source

module.

Check for syntax errors.

Replace all the SQL statements with

CALLs in the host language, to give a

modified source module.

Construct a Data Base Request

Module from the SQL statements it

encountered.

Timestamp the modified source

module and the DBRM.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

21/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 21 of 33 21


Precompiler (Contd..)

The DBRM becomes input to the

BIND component.

Does not access the DB2 Catalog.

Can add code from Libraries.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

22/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 22 of 33 22


Bind

Compiles one or more DBRMs toproduce an application plan or a

package

The plan represents compiled form of

the original SQL statements form

which the DBRMs were built. It includes calls on the Data Manager

component of Database Services.

Checks for errors, using the DB2

Catalog.

Checks for authorization.

Selects optimized access path.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

23/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 23 of 33 23

Package

Single bound DBRM with optimized

access path.

If one DBRM used in the plan is changed

only that Package needs to be rebound.

New packages can be bound to thepackage collection without binding the

plan.

Each package is assigned to exactly one

collection when it is bound.

Collections are essentially just a means

of giving a name to a logically related set

of packages.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

24/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 24 of 33 24

Plan

Executable module containing access

path logic produced by DB2 optimizer.

Consists of names of packages and/or

directly bound DBRM(s).

Bind produces such a plan by bindingtogether the specified packages and

DBRMs.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

25/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 25 of 33 25

Packages and Plans:

Previously all of the DBRMs for a given

application were simultaneously

compiled into optimized code and bound

together into the required application

plan.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

26/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 26 of 33 26

The disadvantages were :

If an individual DBRM needed to be

recompiled, the entire plan had to be

recompiled and rebound.

If multiple plans involved the same

DBRM, the same DBRM had to be

recompiled multiple times.

If that DBRM ever needed to be

recompiled, then all the relevant plans

had to be recompiled.

Adding a new DBRM to the existing plan

required again a recompilation and

rebind of the entire plan.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

27/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 27 of 33 27

The package concept was introducedas a remedy.

If a given DBRM needs to be recompiled,

all that has do be done is an appropriate

package bind.

If multiple plans involve the same DBRM,

that DBRM can now be compiled once,and the corresponding package

referenced multiple times in multiple plan

binds.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

28/33

7/27/2019 DB2 UNIT 2

29/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 29 of 33 29

7/27/2019 DB2 UNIT 2

30/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 30 of 33 30

Precompiler

Source

Module

DBRMModified

Source

Module

Compiler Bind

Object

Module

Package

List of

Packages

and/or

DBRMs

Other

object

modulesLinkage

Editor

Bind

(Load Module)

(Application Plan / Packages)

Runtime Supervisor

Data Manager

Buffer Manager

(Other)

Application

Plan

DB

Load

Module

Main Memory

(One per

Source

module)

(Logically

Part of

Collection)

7/27/2019 DB2 UNIT 2

31/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 31 of 33 31

Parsing, Syntax Checking

Optimization

(Access Path Selection)

Authorization Checking

Plan

Bind

DBRM Catalog

Application

Plan

Package

Package

Bind

List ofPackages

Listing

Diagnosticsetc.

Listing

Diagnostics

etc.

Plan Generation

Authorization

Checking

Stored in Directory

Stored in Directory

7/27/2019 DB2 UNIT 2

32/33

DB2_Tr Ver. 1.0.0 04/12/1998 Page 32 of 33 32


Runtime Supervisor (RS)

RS is resident in main storage whenthe application program is executing.

Its job is to oversee the program

execution.

When the application program

requests some DB operation:

Control goes first to the RS

The RS uses the control information

in the plan to request the appropriate

operations on the part of the Data

Manager.

DB2 (Contd..)

7/27/2019 DB2 UNIT 2

33/33


Data Manager

It performs all of the normal access

method functions

i.e. search, retri eval, update, and so

on.

In short, this component manages the

physical database(s)

Buffer Manager

Physically transfer data between the

external medium and virtual storage;in effect, it performs the actual I/O

operations.

DB2 (Contd..)

db2 unit 2

Documents