VSAM- Basic Concepts -V2.0

1z/OS VSAM Concepts

2Sessions Outline - Day 3 Session 1 : Introduction to VSAM

Session 2 : Structure of VSAM Datasets

Session 3 : Access Method Services

Session 4 : Demo/Exercise Discussion

3Objectives

Familiarization with

VSAM concepts

Space Allocation and types of data sets supported by VSAM

VSAM Characteristics

Identify the general uses for Access Method Services

4Introduction to VSAM (Virtual Storage Access Method)

Session 1

5Topics Covered VSAM Basics

VSAM Dataset Organization

6What is VSAM? VSAM is a high-performance access method used in OS/390, MVS/ESA

and z/OS operating systems

Used as a Dataset in conjunction with programming languages (COBOL or PL/I) to create Applications

Used by CICS to store and retrieve data

Not a database management system does not provide a relationship among data (such as DB2 or IMS)

7VSAM Characteristics VSAM supports three types of data access: Sequential, Random (also

called Direct access) and Skip Sequential

Protection of data against unauthorized access is an inherent part of VSAM

Easily portable to AS/400, the PC or non-IBM computers (cross system compatibility)

A format for storing data independently of the type of direct access storage device on which it is stored

8VSAM Characteristics (Contd.) Options for optimizing performance

A multifunction service program (Access Method Services - IDCAMS) for setting up catalog records and maintaining data sets

Transactional VSAM - allows VSAM data set sharing in batch/online and batch/batch environments

9VSAM Dataset Organizations

ESDS Entry Sequenced Data Set

KSDS Key Sequenced Data Set

RRDS (Fixed Length) Relative Record Data Set

VRRDS Variable Length Relative Record Data Set

LDS Linear Data Set

10

NON-VSAM Access Methods

BSAM : Basic Sequential Access Method

QSAM : Queued Sequential Access Method

ISAM : Indexed Sequential Access Method

BDAM : Basic Direct Access Method

11

Similarities between VSAM & NON-VSAM Datasets

VSAM type Similar to

KSDS ISAM

ESDS BSAM/QSAM

RRDS BDAM

12

VSAM Dataset Organization

13

Topics Covered VSAM Catalog Structure

VSAM Terminology

VSAM Record Storage Control Intervals and Control Areas

14

VSAM Terminology

Catalog Management

Logical Record

Key Field

Physical Record

Cluster

Sphere

Index component

Record management

Data component

Master/User Catalog

Data Space

Control Interval and Control Area

Alternate Indexes

Spanned Records

15

Catalog Management

VSAM maintains extensive information about data sets and direct access

storage space in an integrated catalog facility (ICF) catalog.

The catalogs collection of information about a data set defines that data

sets characteristics. All VSAM files

must be defined in an ICF catalog.

16

Record Management

The record management part of VSAM contains the access method code.

17

Logical record

Unit of information used to store data in a VSAM data set.

Set of bytes containing a logical description of an item processed

by an application program.

A logical record can be of a fixed size or a variable size depending on the

business requirements.

18

Key field

Identifies the item associated with the logical record.

Important Field whose contents can be used to retrieve the specific logical

record

19

Physical record

The data is usually a set of logical records (packed together) transferred from or to memory by just one Read or Write CCW. The access method uses the BLKSIZE parameter to determine the length of the physical record. A large block size results in fewer gaps in the track but larger buffer in memory to keep the data.

A physical record is device dependent, its size is calculated at the time the data set is defined.

All physical records have the same length.

20

Cluster

Collection of physical datasets that make up one logical data set.

Consists of Data Component or Data Component & Index Component

21

Sphere A sphere is a base VSAM cluster and its associated clusters.

These associated clusters are the alternate indexes (AIXs) of the base cluster.

22

Data and Index Component

A component is an individual part of a VSAM data set. Each component has a name, an entry in the catalog and an entry in the VTOC.

The KSDS and VRRDS organizations have data and index components. ESDS, RRDS and LDS organizations only have data components.

The data component is the part of a VSAM data set, alternate index, or catalog that contains the data records.

Using the Index component VSAM is able to randomly retrieve a record from the data component when a request is made for a record with a certain key. The key determines the records position in the data set.

23

Control Interval and Control Area It is the fundamental building block of every VSAM file.A CI is a contiguous

area of direct access storage that VSAM uses to store data records and control information that describes the records.

A CI is the unit of information that VSAM transfers between the storage device and the process or during one I/O operation. Whenever a record is retrieved from direct access storage, the entire CI containing the record is read into a VSAM I/O buffer in virtual storage. The desired record is transferred from the VSAM buffer to a user-defined buffer or work area.

A CA is formed by two or more CIs put together into fixed-length contiguous areas of direct access storage. A VSAM data set is composed of one or more CAs. CAs are needed to implement the concept of splits. The size of a VSAM file is always a multiple of its CA. VSAM files are extended in units of CAs. A spanned record cannot be larger than a CA.

24

Alternate Indexes

Alternate indexes (AIXs) allows logical records of a KSDS or of an ESDS to

be accessed sequentially and directly by more than one key field.

AIXs eliminate the need to store the same data in different sequences in

multiple data sets for the purposes of various applications. Each alternate

index is a KSDS cluster consisting of an index component and a data

component.

25

Spanned Records Spanned records are needed when the application requires very long logical

records. A spanned record may be the data component of an AIX cluster. If spanned records are used for KSDS, the primary key must be within the first control interval.

Spanned records are logical records that are larger than the CI size. To have spanned records, the file must be defined with the SPANNED attribute at the time it is created. Spanned records are allowed to extend across or span control interval boundaries.

A spanned record must always begin on a control interval boundary and fills one or more control intervals within a single control area. A spanned record cannot share the CI with any other records.

26

Control Intervals and Control Areas

27

Control Interval VSAM Basic unit of work the minimum amount of data that is transferred

via buffers, between DASD and Main Memory

VSAM determines the size of the physical Record (BLOCK) based on CI Size

The CI size can be from 512 byes to 32 KB

28

Control Interval & Control Area CA is a fixed length area of auxiliary storage space in which VSAM stores

records

Logical records of a VSAM dataset are grouped into a number of CIs.

CIs of a dataset are grouped into one or more CAs

The size of a VSAM file is always a multiple of its CA

29

General format of a Control Interval

30

Format of Data Control Interval

Record1 Record2 Record3 Free Space (FSPC)

Logical Record Area (LRA)Unused Space

Control Information Field

CISZ

US CIF

31

Control Information Field of a CICIF consists of two subfields: Control Information Definition Field (CIDF)

It is a 4 byte field Contains the Offset and Amount of Free space

Record Definition Field (RDF) It is a 3-byte field. Length of records (based on the spread of data) Number of adjacent records that are of same length

32

Control Information Fields in a CI

Record Type Number of Records/CI Control Information (bytes)

Fixed Length Multiple 10

Fixed Length 1 7

Variable Length Depends on the spread of records

4 (CIDF) and 3 (RDF)

33

CISZ (CI Size) an example How many 80 byte Fixed Length recs can be fit in a CISZ(4096) of

Freespace(20,10) ?

Solution:

40 records of 80 byte record lengthSpace utilized = 40*80 = 3200 bytes US67 bytes

CIF10 bytes

FSPC(4096*0.20) 819 bytes

Unused space = 4096 3200 819 10 = 67

Logical Record Area (LRA)

34

Inserting a record in a CI

11111

Before Inserting:

US CIF

New Record with key 44444

22222 55555 (FSPC)

After Inserting:

US CIF11111 22222 44444 55555 (FSPC)

New record

35

Control Interval Split

Before CI Split:New Record with key 33333

11111 US CIF

US CIF(FSPC)

CI-1

CI-2

22222 44444 55555 66666

After CI Split:

US CIF

US CIF

CI-1

CI-2

11111 22222 33333

44444 55555 66666

(FSPC)

(FSPC)

36

Format of Index Control Interval

Header Entry1 Entry2 Entryn

Control Information Field

KSDS Control Interval

CIF

37

Structure of VSAM Datasets

Session 2

38

Topics Covered Types of VSAM Datasets

More on KSDS Index Structure

39

Objective

Understand the types and internal organization of VSAM datasets

Identify appropriate applications for VSAM data sets

Understand KSDS Index Search Techniques

40

Types of VSAM Datasets

41

VSAM Datasets Types

Entry Sequenced Data Set (ESDS)

Relative Record Data Set (RRDS)

Key Sequenced Data Set (KSDS)

Variable Length Relative Record Data Set (VRRDS)

Linear Data Set (LDS)

42

ESDS CA Structure

43

COBOL example ESDS data set

SELECT ASSIGN TO ORGANIZATION IS SEQUENTIALACCESS MODE IS SEQUENTIALFILE STATUS IS STATUS-KEY

44

RRDS Structure

45

COBOL example - Sequential Retrieval

SELECT ASSIGN TO ORGANIZATION IS RELATIVEACCESS IS SEQUENTIALRELATIVE KEY IS RR-NUMBER

46

COBOL example - Direct Retrieval

SELECT ASSIGN TO ORGANIZATION IS RELATIVEACCESS IS RANDOMRELATIVE KEY IS RR-NUMBER.

47

KSDS Structure

48

COBOL example - Sequential Retrieval

SELECT ASSIGN TO ORGANIZATION IS INDEXEDACCESS IS SEQUENTIALRECORD-KEY IS EMP-NUMFILE-STATUS IS STATUS-KEY.

49

COBOL example - Direct Retrieval

SELECT ASSIGN TO ORGANIZATION IS INDEXEDACCESS IS RANDOMRECORD-KEY IS EMP-NUMFILE-STATUS IS STATUS-KEY.

50

LDS Structure

51

Comparison of VSAM DS

52

Comparison of VSAM DS (Contd.)

53

More on KSDS Index Structure

54

KSDS Structure

55

General Format of Index Set

56

General format of Sequence Set

57

Index Search Techniques

Horizontal Search

For a Sequential Search, search is performed with the key value less than or equal to the sequence set record

Vertical Search

For a Random Access, search is performed from the Index set

Once the key

58

Example-1How Index & Sequence Sets work

59

Example-2Data Component Structure

Data Records

60

Example-2 (Contd.) Data Component Structure

Index Set Record

61

Share option in VSAM

Share option in VSAM is defined as Concurrent Usage of Dataset by several People at the same time. We can use this option for sharing the files in the same region and in other system. The SHAREOPTION has two parameters, the inter-system parameter and intra-system parameter.

Syntax:SHAREOPTIONS(crossregion,crossystem)

62

Share option cont:.... If the source data set is allocated with DISP=SHR, there is a risk that it could be updated by a region other than the FOR. If this happened, the data table would no longer match the source data set. To minimize this risk, the VSAM cross-region SHAREOPTION should be set to 1 or 2. 1 means that either one region can have update access to the data set or many regions can have read-only access. 2 means that one region can have update access to the data set and, at the same time, many regions can have read-only access.

Regardless of the setting of DISP, a warning message is issued if the cross-region SHAREOPTION is 3 or 4, or if it is 2 but the CICS-maintained data table has read-only access (which means another region might be able to update the data set).

63

Syntax and attributes

64

Access Method Services

Session 3

65

Topics Covered

Introduction to IDCAMS

IDCAMS Commands

Define and Load a VSAM dataset

VSAM Advanced Topics

66

Objectives

Use Access Method Services (AMS )

Identify some useful AMS Commands

Define and Load a Basic Cluster with IDCAMS

Define and Build Alternate Index

67

Introduction to IDCAMS

68

IDCAMS Utility

Multifunction utility program supplied with VSAM (IDCAMS) to manage

and maintain datasets

69

IDCAMS Features

IDCAMS can be used to Define, Alter and Delete datasets and allocate space for them List and Maintain VSAM Catalogs Load, Print and Copy datasets Reorganize datasets Define and build alternate indexes Facilitate backup and recovery Provide security and integrity functions

70

Invoking IDCAMS

//YOURJOB JOB (ACCT),'IDCAMS JOB',//STEP1 EXEC PGM=IDCAMS//SYSPRINT DD SYSOUT=*//SYSIN DD *AMS commands and their parameters/*

1. As a Job or Job step Example

71

Invoking IDCAMS (Contd.)2. TSO can be used with VSAM and access method services to

Execute access method services commands Execute a program to call access method services

3. From an application Program

72

IDCAMS Commands

73

COMMANDS

Modal Commands Used to control execution and establish options Modal commands allow the conditional execution of functional

commands.

Functional Commands Used to invoke access method services

74

COMMANDS (Contd..1)

COMMAND specifies the type of service requested

Default statement margins are positions 2 through 72.

Command stmt can be continued to the next line with - as the last parameter

Comment may be embedded in Command statements between /* and */

75

COMMANDS (Contd..2)

76

Condition Codes

IDCAMS returns a condition code following the execution of each Command

Can be used to selectively execute or skip subsequent commands

Initialized to zero at the start of the execution

77

Condition Codes (Contd..1)

LASTCC - specifies the condition code value that resulted from the immediately preceding function command

MAXCC - specifies the maximum condition code value that has been established by any previous function command

78

Condition Codes (Contd..2)

Code Explanation 0 Function executed successfully

4 Some problem was met in executing the function but it waspossible to continue. The continuation might not provideexact results, but no permanent harm will have been done

79

Condition Codes (Contd..3)Code Explanation8 A requested function was completed but major specifications

were unavoidably bypassed

12 The requested function could not be performed, as a result of a logical error

16 A severe error occurred that caused the Job Step to terminate

80

Modal Commands

IF-THEN-ELSE :

Used to control command execution on the basis of condition codes

DO-END :

Used to specify the group of commands as a single unit

81

Modal Commands (Contd.)NULL : Used to indicate that no action is to be taken

PARM : Specifies processing options to be used during execution

SET : Used to change or reset a previously defined condition code

82

Modal Commands - Syntax

IF {LASTCC|MAXCC} {operator} {numeric value}THEN {command }

DO{command set}

ENDELSE {command}

DO{command set}

END

83

Functional Commands

DEFINE Used to define the following objects Alias Alternate index Cluster Dataspace User Catalog and Master Catalog Path Catalog entry for a Generation Data Group Catalog entry for a non-VSAM dataset

84

Functional Commands (Contd..1) DELETE Used to delete catalogs, VSAM and non-VSAM datasets

EXAMINE Analyzes and reports on the structural consistency of the index component and/or data component of KSDS cluster

LISTCAT Used to list catalog entries

85

Functional Commands (Contd..2)

IMPORT Connects user catalogs and imports VSAM datasets

EXPORT Disconnects user catalogs and exports VSAM datasets.

PRINT Used to print VSAM and non-VSAM datasets and catalogs

86


ALTER - Used to alter attributes of datasets and catalog that have already been defined

Alter

Freespace

Volume

Prevent temporary updates to a VSAM dataset

87


BLDINDEX - Builds alternate indexes for existing datasets

Keys will be actually built from the base cluster with the BLDINDEX command

VERIFY : Used to cause a catalog to correctly reflect the end of a dataset after an error occurred in closing a VSAM dataset. The error may have caused the catalog to be incorrect.

88


REPRO

Loads an empty VSAM cluster with records

Creates backup of a VSAM dataset on a sequential dataset and restores the

dataset

Merges data from two VSAM datasets

89

Example: Modal & Functional Commands//JOBNAME JOB ...//STEP1 EXEC PGM=IDCAMS//SYSPRINT DD SYSOUT=*//SYSIN DD *DEFINE CLUSTER -IF LASTCC = 0 THEN -REPRO -ELSE -DOSET LASTCC = 0DELETE CLUSTER ...DEFINE CLUSTER ...END/*

90

Define and Load a VSAM Dataset

91

DEFINE CLUSTER The DEFINE CLUSTER command can be used to define a cluster and

specify attributes for the cluster as a whole and for the components of the cluster. The general format is :

92

DEFINE CLUSTER example//JOB1 JOB CLASS=A//DEFINE EXEC PGM=IDCAMS//SYSPRINT DD SYSOUT=*//SYSIN DD *DEFINE CLUSTER -(NAME(TRGXXX.MAST.CLUSTER) -TRACKS(51) -CONTROLINTERVALSIZE(4096) -INDEXED -VOLUMES(TRG001) KEYS(6,0) -FREESPACE(10,10) -DATA -(NAME(TRGXXX.MASTER.DATA) -TRACKS(21) -RECORDSIZE(200 200)) -INDEX -(NAME(TRGXXX.MASTER.INDEX) -IMBED)./*

93

LISTCAT

The LISTCAT command lists catalog entries.

Freespace, CI/CA split, Data Attributes, Statistics. Allocation information

All parameters of the LISTCAT command are optional

LISTCAT can be used under TSO

95

LISTCAT example//JOBTRGXX ...//LISTCAT1 EXEC PGM=IDCAMS//SYSPRINT DD SYSOUT=A//SYSIN DD *LISTCAT -ENTRIES(TRGXXX.MAST.CLUSTER) -CLUSTER -ALL/*

96

REPRO The REPRO command copies VSAM and non-VSAM data sets, copies

catalogs.

97

REPRO SyntaxREPRO {INFILE(ddname)/password INDATASET(entryname)/password {OUTFILLE(ddname/passwordOUTDATASET(entryname/password}( CHARACTER | DUMP | HEX )( FROMKEY(key) | ( FROMADDRESS(address) |( FROMNUMBER(number) )SKIP(number) ( TOKEY(key) |TOADDRESS(address) |TONUMBER(number) )COUNT(Number)

98

REPRO example

//JOBTRGXX ...//STEP1 EXEC PGM=IDCAMS//INPUTDD DD DSN=TRGXXX.DATA.RECORDS,DISP=OLD//SYSPRINT DD SYSOUT=A//SYSIN DD *REPRO -INFILE(INPUTDD) -OUTDATASET(TRGXXX.KSDS.CLUSTER)/*

Example: Load VSAM KSDS from Non-VSAM dataset and copy selected records to an ESDS

99

DELETE The DELETE command deletes catalogs, VSAM datasets, non-VSAM

datasets and objects.

101

DELETE example

//DELMAST EXEC PGM=IDCAMS//SYSPRINT DD SYSOUT=A//SYSIN DD *DELETE -(TRGXXX.MAST.CLUSTER -TRGXXX.TEST.DATA) -FILE(DD1) -PURGE -ERASE/*

102

PRINT

PRINT: The PRINT command prints VSAM datasets, non-VSAM datasets, and catalogs. The syntax is:

103

PRINT SyntaxPRINT {INFILE(ddname /password )INDATASET(entryname /password ) }CHARACTER| DUMP | HEXFROMKEY(key) | FROMADDRESS(address) | FROMNUMBER(number) }SKIP(number) OUTFILE(ddname) TOKEY(key) |TOADDRESS(address) |TONUMBER(number)|COUNT(Number)

104

PRINT example//JOBTRGXX ...//DEFAIX EXEC PGM=IDCAMS//SYSPRINT DD SYSOUT=A//SYSIN DD *PRINT -INDATASET(TRGXXX.MAST.CLUSTER) -FROMKEY(E00001) -COUNT(100)/*

105

VERIFY The VERIFY command causes a catalog to correctly reflect the end of a

VSAM data set after an error occurs while closing a VSAM data set

The syntax is:VERIFY {FILE(ddname/password) |DATASET(entryname/password)}

106

VERIFY ExampleExample of a typical VERIFY usage Job TRGJJJJ has terminated abnormally and VSAM dataset

TRGXXX.MAST.CLUSTER is not closed correctly. This job is followed by another job that uses this file for an IDCAMS copy. Following are the set of return codes that will appear in the Job Spool

In JESMSGLG the error will beIEC161I 056-084,TRGGXXXX,JS010,IFILE01,,,

In SYSPRINT of the step failed the error will beIDC3300I ERROR OPENING TRGXX.MAST.CLUSTERIDC3351I ** VSAM OPEN RETURN CODE IS 118

Solution: A VERIFY issued on VSAM file TRGXXX.MAST.CLUSTER will correct this error

107

VERIFY Example (Contd..)//JOBTRGXX ...//STEP1 EXEC PGM=IDCAMS//SYSPRINT DD SYSOUT=A//SYSIN DD *VERIFY -DATASET(TRGXXX.MAST.CLUSTER)/*

108

ALTERNATE INDEX Allows for a KSDS to be accessed in a different order other than the primary

key

Allows the creation of an index for a non-indexed object, such as an ESDS cluster

109

Steps to create an ALTINDX DEFINE command to create the alternate index

BLDINDEX command to build the keys for the alternate index

DEFINE command to create a PATH relating the alternate index to the base cluster

110

DEFINE ALTINDX example//JOBTRGXX ...//DEFINE EXEC PGM=IDCAMS//SYSPRINT DD SYSOUT=*//SYSIN DD *DEFINE AIX -(NAME(TRGXXX.MAST.TEMP.AIX) -VOLUMES(TRG001) -RELATED(TRGXXX.MAST.CLUSTER) -UPGRADE -TRACKS(21) -KEYS(24,8) RECORDSIZE(200 200) -FREESPACE(10,10) NONUNIQUEKEY -DATA -(NAME(TRGXXX.MAST.TEMP.AIX.DATA) -INDEX -(NAME(TRGXXX.MAST.TEMP.AIX.INDEX) -)/*

111

BLDINDX The BLDINDEX command builds alternate indexes for existing data sets

Alternate Index can be built only after its base has been loaded with at least one record

112

BLDINDX example

//JOBTRGXX ...//BLDINDEX EXEC PGM=IDCAMS//DD1 DD DSN=TRGXXX.TEMP.SEQ,DISP=SHR //DD2 DD DSN=TRGXXX.MAST.TEMP.AIX,DISP=SHR//IDCUT1 DD VOL=TEMPDA,UNIT=3380,DISP=OLD,AMP='AMORG//IDCUT2 DD VOL=TEMPDA,UNIT=3380,DISP=OLD,AMP='AMORG' //SYSPRINT DD SYSOUT=*//SYSIN DD *BLDINDEX INFILE(DD1) - OUTFILE(DD2) /*

113

DEFINE PATH After defining an alternative index, a PATH must be defined to access the

data set. This forms the connection between the alternative index and the base cluster, and the connection is stored in the catalog

When a program opens a path for processing, both the base cluster and the alternate index are opened

114

DEFINE PATH example

//JOBTRGXX ...//BLDINDEX EXEC PGM=IDCAMS//SYSPRINT DD SYSOUT=*//SYSIN DD *DEFINE PATH ( - NAME(TRGXXX.MAST.TEMP.IX) - PATHENTRY(TRGXXX.MAST.TEMP.AIX) ) /*

115

GDG A group of chronologically or functionally related data sets are called

Generation Data Group (GDG)

Each data set within a GDG is called a Generation Data Set or simply a Generation

They are processed periodically, often by adding a new generation, retaining previous generations, and sometimes discarding the oldest generation

Each generation data set in the group will have the name as GDG name.GxxxxVyy, where xxxx is the generation number and yy is the version number

116

GDG (Contd..) GDGs can be referred in a JCL by means of an absolute name or relative

name

Absolute name is by coding the complete Generation name as GDGname.G0001V00

Relative name is a signed integer used to refer to the latest (0), the next to the latest (1), and so forth, generation. The relative number can also be used to catalog a new generation (+1)

117

GDG Advantages The advantages of grouping related data sets are:

All of the data sets in the group can be referred to by a common name

The operating system is able to keep the generations in chronological order

Outdated or obsolete generations can be automatically deleted by the operating system

118

GDG Usage One of the important usage of a GDG is for cataloging periodic backups of

VSAM datasets Example, a GDG of limit 7 can be used to take backup of VSAM data

sets from the batch job for all 7 days of the week The GDG base after data sets are cataloged will be as follows

GDGname.G0001V00 GDGname.G0001V01 GDGname.G0001V06

Another important usage of GDG is for cataloging periodic reports (weekly, monthly, etc). Example, a GDG with limit 12 can hold monthly reports for a year

119

GDG SyntaxDEFINE GENERATIONDATAGROUP

(NAME(entryname) LIMIT(limit) [EMPTY | NOEMPTY] [SCRATCH | NOSCRATCH] [TO(date) | FOR(days)])

120

GDG example//JOBTRGXX ...//DEFGDG EXEC PGM=IDCAMS//SYSPRINT DD SYSOUT=A//SYSIN DD *DEFINE GENERATIONDATAGROUP (- NAME(TRGXXX.MAST.GDG) - LIMIT(5) - SCRATCH ) /*

121

VSAM Backup considerations

//JOBTRGXX ...//LOADSTEP EXEC PGM=IDCAMS//SYSPRINT DD SYSOUT=A//DD1 DD DSN=TRGXXX.MAST.GDG(+1),// DISP=(NEW,CATLG,DEL),UNIT=TAPE,// VOL=TEMPAD,DCB=(RECFM=FB,LRECL=80)//SYSIN DD *REPRO -

INDATASET(TRGXXX.MAST.CLUSTER) - OUTFILE(DD1) /*

122

Utility U.5 in ISPF

A user interface is available under option U.5. This provides 2 options Access method services VSAM maintenance utility

123

U.5.1 OptionAccess method services (option u.5.1) provides interface for the following functions

Define Cluster Define alternate index Define path Alter VSAM dataset characteristics Rename a dataset Copy/Load a VSAM dataset Delete a VSAM dataset Print a VSAM dataset Verify endfile markers

124

VSAM Advanced Topics

125

CICS VSAM Transparency for z/OS CICS VSAM Transparency for z/OS can help you unlock value in data used

by your legacy applications and extend its use to new DB2 applications, online and e-business

126

VSAM to DB2 migration 24x7 availability

Running adhoc queries

Ability to perform data analysis (mgt reporting, analytics)

Exploitation of database maintenance tools

Integration with new applications based on DB2 technology

127

Other advanced topics in VSAM

VSAM Extended Format & Extended Addressability

Data striping

Data compression

Partial space release

System-managed buffering (SMB)

VSAM Record Level Sharing (RLS)

Utilities: File-Aid, DITTO, STARTOOL

128

Discussion Topics

What does an index component contain in KSDS ?

How data is organized in Data Component ?

What is the Index search technique for a Random process?

Access Method Services, IDCAMS creates and maintains VSAM DS. State

True / False

129

Discussion topics (Contd.)

The number of extents that the VSAM can grow up to : a) 123 b) 251 c) 255

d) none

What is Alternate Index ?

How is Alternate Index created ?

How does the BLDINDX perform ?

How is an LDS different from an ESDS?

130

Demo/Exercise

Session 4

131

Demo

Create a VSAM KSDS

Load VSAM KSDS (Use Repro)

Create an Alternate Index

Build Index

Define Path

Do a LISTCAT on KSDS and explain the output

132

References MVS/VSAM for the Application Programmer Gary D.Brown & S.A.M.

Smith

VSAM Demystified Mary Lovelace et al. IBM Redbooks 2003 (Document Number SG24-6105-01) in IBMs Website

DFSMS/MVS V1R2 Access Method Services for VSAM (Document Number SC26-4905-01) in IBMs Website

133

THANK YOU

PowerPoint PresentationSessions Outline - Day 3ObjectivesIntroduction to VSAM (Virtual Storage Access Method)Topics CoveredWhat is VSAM?VSAM CharacteristicsVSAM Characteristics (Contd.)VSAM Dataset OrganizationsNON-VSAM Access MethodsSimilarities between VSAM & NON-VSAM DatasetsVSAM Dataset OrganizationSlide 13VSAM TerminologyCatalog ManagementRecord ManagementLogical recordKey fieldPhysical recordClusterSphereData and Index ComponentControl Interval and Control AreaAlternate IndexesSpanned RecordsControl Intervals and Control AreasControl Interval Control Interval & Control AreaGeneral format of a Control IntervalFormat of Data Control IntervalControl Information Field of a CIControl Information Fields in a CICISZ (CI Size) an exampleInserting a record in a CIControl Interval SplitFormat of Index Control IntervalStructure of VSAM DatasetsSlide 38ObjectiveTypes of VSAM DatasetsVSAM Datasets TypesESDS CA StructureCOBOL example ESDS data setRRDS StructureCOBOL example - Sequential RetrievalCOBOL example - Direct RetrievalKSDS StructureSlide 48Slide 49LDS StructureComparison of VSAM DSComparison of VSAM DS (Contd.)More on KSDS Index StructureSlide 54General Format of Index SetGeneral format of Sequence SetIndex Search TechniquesExample-1 How Index & Sequence Sets workExample-2 Data Component StructureExample-2 (Contd.) Data Component StructureShare option in VSAMShare option cont:....Syntax and attributesAccess Method ServicesSlide 65Slide 66Introduction to IDCAMSIDCAMS UtilityIDCAMS FeaturesInvoking IDCAMSInvoking IDCAMS (Contd.)IDCAMS CommandsCOMMANDSCOMMANDS (Contd..1)COMMANDS (Contd..2)Condition CodesCondition Codes (Contd..1)Condition Codes (Contd..2)Condition Codes (Contd..3)Modal CommandsModal Commands (Contd.)Modal Commands - SyntaxFunctional CommandsFunctional Commands (Contd..1)Functional Commands (Contd..2)Functional Commands (Contd..3)Functional Commands (Contd..4)Functional Commands (Contd..5)Example: Modal & Functional CommandsDefine and Load a VSAM DatasetDEFINE CLUSTERDEFINE CLUSTER exampleLISTCATLISTCAT SyntaxLISTCAT exampleREPROREPRO SyntaxREPRO exampleDELETEDELETE Command Syntax DELETE examplePRINTPRINT SyntaxPRINT exampleVERIFYVERIFY ExampleVERIFY Example (Contd..)ALTERNATE INDEXSteps to create an ALTINDXDEFINE ALTINDX exampleBLDINDXBLDINDX exampleDEFINE PATHDEFINE PATH example GDG GDG (Contd..) GDG Advantages GDG Usage GDG SyntaxGDG exampleVSAM Backup considerationsUtility U.5 in ISPFU.5.1 OptionVSAM Advanced TopicsCICS VSAM Transparency for z/OS VSAM to DB2 migrationOther advanced topics in VSAM Discussion TopicsDiscussion topics (Contd.)Demo/ExerciseDemo ReferencesTHANK YOU

Documents

VSAM- Basic Concepts -V2.0