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Information Management - PowerPoint Presentation

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Information Management - PPT Presentation

System DB Concepts amp Programming Files Vs Databases Networked Hierarchical amp Relational structure Access types HSAM HISAMHDAMHIDAMVSAM IMS DB an Hierarchical Structure ID: 482930

type segment bytes pic segment type pic bytes pcb database field parent index start sru program data call access

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Slide1

Information Management System DB Concepts & Programming

Slide2

Files Vs DatabasesNetworked, Hierarchical & Relational structure

Access types - HSAM, HISAM,HDAM,HIDAM,VSAM

IMS DB - an Hierarchical StructureDatabase Definitions - DBDProgram Specification Block ,Program Control Block DL/I Calls - Data Retrieval and ManipulationDL/I FunctionsQualified/ Unqualified Calls, SSAs, Command CodesDL/I Status codes

Basic

TopicsSlide3

Advanced TopicsData Sensitivity - Segment Level & Field levelCheckpoint & Restart

IMS DB in CICS Environment

Secondary IndexingDifference between MPP, BMP, DLIUsing ‘HFCTDLI’Slide4

File Vs DatabasesData more redundant Redundancy avoidedDuplicate data

Minimize

DuplicatesData insecure Security providedNo control over data Field level sensitivityThreat to Integrity Consistency of dataLack of inbuilt Data Logging, recovery features Commits & Rollbacks

Lack of data Locks Automatic locksSlide5

Database StructuresNetwork Structures (e.g IDMS)

Many to Many relationships

Complex structure using PointersBest for Keeping storageHierarchical Structures (e.g IMS DB)

One to Many Relationships

Inverted Tree like Structure

Best for storing parent and child type entities

Relational Structures (e.g DB2)

One to Many, Many to One

Best for ease of data retrievalSlide6

Access TypesHSAM/SHSAM (Simple /Hierarchic sequential Access Method)

The segments that make up the database record are related to one another by their physical locations (SHSAM has only root occurrences)HISAM/SHISAM (Simple / Hierarchic Indexed Sequential Access Method)

The data is stored with hierarchic sequential organization along with an index

for

random processing (SHISAM has only index of root occurrences)

HDAM (Hierarchic Direct Access Method

)

The segment occurrences include prefixes that contain the direct address

pointers to related segment - stores root segment

occurrences

HIDAM (Hierarchic Indexed Direct Access Method

)

Similar to HDAM but stores an index of the root segment occurrencesSlide7
Slide8

Basic IMS TerminologiesSRCS Units

2

1

3

Clients

Employ

Projects

Salary

Root

Segment

Parent Segment

Child Segment

Segment

Level

Segment Occurrence

Path

Database Record

Twins

Sequential Processing

Random Processing

SRCS

Information

Database

Client Info

Project InfoSlide9

DefinitionsSegment

- Unit of Information handled in IMS

- Unit of data transferred from DL/I in an IO operation - Consists of fields, key fields & Search fieldsOccurrence

- Specific segment of a particular type of segment

- Contains actual user data

Root Segment

- Top of the hierarchy

- All other segments are derived from the root

Parent Segment

- Segment that has dependent segmentsSlide10

Definitions (contd)Child

Segment

- A dependent segmentSegment Level - Depth of an IMS structure - Root is at Level 0, max 15 levels, max 255 segments

Path

- Series of segments from Root to the child

Database record

- Each occurrence of the Segment Plus all

occurrence of the subordinate segments

Twins

- Segment occurrences of same type with same parent

segment occurrenceSlide11

IMS Control BlocksIMS PGM1

IMS

PGM2

DL/I

CONTROL

UNIT

DBD1

DBD2

DBD3

PCB for DB1

PCB for DB2

PCB for DB3

PSB

DBDs

IMS DBs

DB1

DB2

DB3Slide12

DBD : Names the database and identifies the access method DBD Name = SRCS, ACCESS=(HIDAM,VSAM)DATASET : Specifies DD Name used in the JCL and other parameters DATASET DD1=DDSAT,DEVICE=3380,SIZE=(4096),FRSPC=(0,15)SEGM : Names the segment. Identifies the parent and establishes the length

SEGM Name =SRU,PARENT=0,BYTES=40

LCHILD : Names the logical segment used in secondary Indexing and Logical database LCHILD NAME=(SRUNAME,SRCS1),PTR=INDXFIELD : Defines fields. And identifies search &key fields by SEQ parameter FIELD NAME=(SRUCODE,SEQ,U)BYTES=3,START=1,TYPE=CDBDGEN: Indicates the end of the DBDGEN process DBDGENCOMMENT: ‘*’ IN 3rd COLUMN for writing user comments

DBD : Database Description, describes physical Database

DBDGEN : DBDGEN Utility, Describes the physical structure of

the Database and creates DBDSlide13

Sample DBD Listing for SRCS Info Database

DBD NAME=SRCS,ACCESS=(HIDAM,VSAM)DSG1 DATASET DD1=DDSAT,DEVICE=3380,SIZE=4096,FRSPC=0,15) SEGM NAME=SRU,PARENT=0,BYTES=40 FIELD NAME=(SRUCODE,SEQ,U),BYTES=3,START=1,TYPE=P FIELD NAME=SRUNAME,BYTES=5,START=4,TYPE=C FIELD NAME=SRULOC,BYTES=12,START=9,TYPE=C FIELD NAME=SRUHEAD,BYTES=20,START=21,TYPE=C SEGM NAME=CLIENT,PARENT=SRU,BYTES=45 FIELD NAME=(CLTID,SEQ,U),BYTES=4,START=1,TYPE=P FIELD NAME=CLTNAME,BYTES=10,START=5,TYPE=C FIELD NAME=CLTLOC,BYTES=11,START=15,TYPE=C FIELD NAME=CLTHEAD,BYTES=20,START=26,TYPE=C Slide14

SEGM NAME=PROJECT,PARENT=CLIENT,BYTES=35 FIELD NAME=(PRJID,SEQ,U),BYTES=4,START=1,TYPE=P FIELD NAME=PRJNAME,BYTES=5,START=5,TYPE=C FIELD NAME=PRJTMSIZE,BYTES=4,START=10,TYPE=C FIELD NAME=PRJHEAD,BYTES=22,START=14,TYPE=CSEGM NAME=EMPLY,PARENT=SRU,BYTES=40 FIELD NAME=(EMPID,SEQ,U),BYTES=5,START=1,TYPE=P FIELD NAME=EMPNAME,BYTES=10,START=6,TYPE=C

FIELD NAME=EMPPROJ,BYTES=5,START=16,TYPE=C

FIELD NAME=EMPADDR,BYTES=20,START=21,TYPE=CSEGM NAME=SALARY,PARENT=EMPLY,BYTES=35 FIELD NAME=(SALEMPID,SEQ,U),BYTES=5,START=1,TYPE=P FIELD NAME=SALBASIC,BYTES=10,START=6,TYPE=C FIELD NAME=SALHRA,BYTES=5,START=16,TYPE=C FIELD NAME=SALDA,BYTES=5,START=21,TYPE=CDBDGENFINISHENDSlide15

PSB Program Specification Block,describes Logical structure of the Database that a program will use.It contains one or more PCB’s (Program Communication Block).PCB describes one Database.PSBGEN PSBGEN Produces a load module stored in the PSBLIB library and creates PSBMajor Macros UsedPCB : Describes type (DB or DC), name of the DBD, Key length(length of

the longest concatenated key the program can process) and

processing Option (Defines how the segment may be accessed)PCB TYPE=DB,DBDNAME=SRCS,KEYLEN=20,PROCOPT=LSSENSEG : Define the name of the segments in the Database your program needs access toSENSEG NAME=CLIENT,PARENT=SRUSENFLD : Subordinate to the SENSEG macro, only fields that are defined by the SENFLD macro can be accessed from the I/O Area.SENFLD NAME=PROJECT,PARENT=CLIENTPSBGEN PSBNAME=MYPSB,LANG=COBOLEND Slide16

SAMPLE PSB FOR SRCS INFO DB PROJECT REFERENCE PROGRAM PCB TYPE=DB,DBDNAME=SRCS,KEYLEN=10,PROCOPT=LS SENSEG NAME=SRU,PARENT=0 SENSEG NAME=CLIENT,PARENT=SRU SENSEG NAME=PROJECT,PARENT=CLIENT PSBGEN PSBNAME=MYPSB,LANG=COBOL END

SAMPLE PSB FOR SRCS INFO DB PROJECT REFERENCE PROGRAM

PCB TYPE=DB,DBDNAME=SRCS,KEYLEN=10,PROCOPT=LS SENSEG NAME=SRU,PARENT=0 SENSEG NAME=CLIENT,PARENT=SRU SENSEG NAME=PROJECT,PARENT=CLIENT SENSEG NAME=EMPLY,PARENT=SRU SENSEG NAME=SALARY,PARENT=EMPLY PSBGEN PSBNAME=MYPSB,LANG=COBOL END Slide17

DL/I INTERFACE DL/I passes control to your program Uses ENRTY and CALL statement to code DL/I call in the Procedure Division ENTRY ‘DLITCBL’ USING PCB-name1 PCB-name2

This DL/I tells entry of the program for Batch program & MPP program CALL ‘CBLTDLI’ USING DLI-FUNCTION PCB-mask Segment-io-area [segment search arguments (s)] This call is the name of the interface module that link edited with your program’s object module.Slide18

CALL PARAMETERSCALL ‘CBLDTLI’ USING DLI-FUNCTION PCB-mask Segment-io-area [segment search argument (s) ] If we use PL/I language then CBLTDLI will be PLITDLI

Parameter Function

DL/I -Function A four byte code that tells DL/I what kind of call to makePCB-mask Arguments tells DL/I which PCB to use for the callIO-Area Tells DL/I where to put the segmentSSA Gives DL/I additional criteria to use in finding a particular Segment, Can be upto 15 SSA’s Slide19

DL/I FUNCTIONS GU - Get Unique GN - Get Next GNP - Get Next within Parent GHU - Get Hold Unique GHN - Get Hold Next GHNP - Get Hold Next within Parent

ISRT - To Insert

REPL - To replace DLET - To Delete CHKP - To take a Checkpoint at a particular point XRST - To Restart from Particular point previous Checkpoint INIT - To Initialize SYNC - To commit Slide20

PCB MASKDefine in linkage Section and establishes correspondence between linkage Section PSB-mask and PSB’s with in your program.SAMPLE PCB-MASK LAYOUT VARIABLE DESCRIPTION

01 SRCS-PCB-MASK.

03 SR-DBD-NAME PIC X(8). Name of the Database being processed 03 SR-SEG-LEVEL PIC XX. Specifies current segment level in the DB 03 SR-STATUS-CODE PIC XX. Contains data yr program will evaluate after call 03 SR-PROC-OPT PIC X(4). Type of processing the program authorized to do 03 SR-SEG-NAME PIC X(8). Stores name of the segment just proceeded 03 SR-KEY-LENGTH PIC S9(5). Length of the concatenated key 03 SR-NUM-SENSEGS PIC S9(5). No of SENSEG macros subordinate to the PCB 03 SR-KEY-VALUE PIC X(20). Key value retrieved Slide21

I-O AREA LAYOUT FOR SEGMENTS

SRUCODE

SRUNAME

SRULOC

SRUHEAD

01 SRU-AREA.

03 SRU-CODE PIC X(3).

03 SRU-NAME PIC X(5).

03 SRU-LOC PIC X(12)

03 SRU-HEAD PIC X(20).

CLTID

CLTNAME

CLTLOC

CLT-HEAD

01 CLIENT-AREA.

03 CLT-CLTID PIC X(4).

03 CLT-CLTNAME PIC X(10).

03 CLT-CLTLOC PIC X(11)

03 CLT-CLTHEAD PIC X(20).

PROJID

PRJNAME

TMSIZE

PRJADDR

01 PRJ-AREA.

03 PRJ-PROJID PIC X(4).

03 PRJ-PRJNAME PIC X(5).

03 PRJ-TMSIZE PIC X(4)

03 PRJ-HEAD PIC X(20).

EMPID

EMPNAME

EMPPROJ

EMPADR

01 EMP-AREA.

03 EMP-ID PIC X(5).

03 EMP-NAME PIC X(10).

03 EMP-PROJ PIC X(5)

03 EMP-ADR PIC X(20).

01 SAL-AREA.

03 SAL-EMPID PIC X(5).

03 SAL-BASIC PIC X(10).

03 SAL-HRA PIC X(5).

03 SAL-DA PIC X(5).

EMPID

BASIC

HRA

DASlide22

SEGMENT SEARCH ARGUMENT Identifies Segment Occurrence You want to access You may have to code several SSA’s in a single DL/I CALL There are two types of SSA’s Unqualified SSA & Qualified SSA UNQUALIFIED QUALIFIED

Search for a Specific Segment type Searches for a specific occurrence of a

specific segment type Access the database Sequentially Access the database Randomly Identify by segment name and space Identify by segment name and Seg-key Example01 UNSRU-SSA. 01 QUALKBU-SSA. 03 SRU-UNSSA-NM PIC X(8) Value ‘SRU ‘. 03 SEG-NAME PIC X(8) VALUE ‘SRU ‘. 03 FILLER PIC X Value Space. 03 COM-CODE PIC X(2) VALUE ‘*-’. 03 BEGIN-QUAL PIC X VALUE ‘(‘.

03 KEY-NAME PIC X(8) VALUE ‘SRUKEY’.

03 REL-OPR PIC X(2) VALUE ‘= ‘.

03 KEY-VALUE PIC X(20).

03 END-QUAL PIC X VALUE ‘)’. Slide23

COMMAND CODES Command Code Description D Retrieve Path F Access First Segment occurrence L Access Last Segment occurrence

U Maintain current position at this level

V Maintain current position at this level and higher levels Q Enqueue Segment N Do Not replace this Segment C Use a Concatenated Key P Establish Percentage at this level - Null command code / ignore Slide24

DL/I STATUS CODES List of Codes Common Status Codes AB GK GB AC GP End of Database during Sequential retrieval using GN AD II

AH IX GE

AI LB Segment Occurrence as defined in a qualified SSA not AJ LC found or not added in a ISRT due to error in Specified path AK LD AM LE AI AO NO Error in opening the database dataset AT RX AU V1 Spaces DA SPACES Call ended normally DJ DX GA GB GD GESlide25

Data SensitivityDBA At a PSB level for SEGMENTS PROCOPT PCB TYPE=DB,DBDNAME-SRCS,,KEYLEN=11,PROCOPT SENSEG NAME =SRU,PARENT=0 SENSEG NAME =CLIENT,PARENT=SRU Processing Options : G, I, R, D, A, P, O, N, T, E, L, GS, LS, H

At a PSB level for fields Done by DBA by use of SENFLD macro , specifying those fields that can be changed.Programmer At PROGRAM Level - Qualified SSA call with Command code N (No Replacement)Slide26

Checkpointing & Restart A point in the program where the database changes the program made are Considered complete and accurate -written to a DL/I log Used for Recovery Process Are of two types - Basic Checkpointing and Symbolic Checkpointing Basic Checkpointing

CALL ‘CBLTDLI’ USING DLI-CHKP,

I-O-PCB-MASK, CHECKPOINT-ID. Symbolic Checkpointing Stores program data along with checkpoint records and retrieves that data when program restarts after failure. For extended Restart , an XRST call to be issued with the same fields as in CHKP call. It allows DL/I to retrieve the value in checkpoint record and restores the specified fields.Slide27

Explosive Mix - IMS DB with CICS Scheduling Call CICS Region / Partition

User Task

User Interface Block

(UIB)

Program Communication

Block

(PCB)

A DL/I task must establish addressability to UIB and one or more PCBSlide28

IMS & CICS ContinuedCALL ‘CBLTDLI’ USING FUNC-INIT PSB-NAME ADDRESS OF DLIUIB

SET ADDRESS OF PCB-ADDR-LIST TO UIBPCBAL

SET ADDRESS OF PCB-1 TO PCB-1-ADRSET ADDRESS OF PCB-2 TO PCB-2-ADR…...

User Interface Block

Address of PCB List

Address of PCB 1

Address of PCB 2

PCB Address list

PCB1

PCB2Slide29

Secondary Indexing

Employee Index Database

EMP..Seg

Addr

Employee ID

Index Pointer Segment

SRU

CLIENTS

EMPLOYEE

PROJECTS

Index Source Segment

Index Target

Segment

Same index Source segment and index target segmentSlide30

Secondary Indexing Continued

Employee Index Database

SRU..Seg

Addr

Employee ID

Index Pointer Segment

SRU

EMPLOYEE

Index Source Segment

Index Target

Segment

Different index Source segment and index target segment

CLIENTS

PROJECTSSlide31

Secondary Indexing Continued Alternate sequencing is provided by storing pointers to Segments of the indexed Database in a separate secondary index data base Secondary index data base has only one segment type - the Index pointer segment which in turn contains a prefix element and a data element

Prefix element points to the index target segment

Secondary indexing is useful for accessing segments were both Index source segment and index target segment are same Index source segment and index target segment are different Two DBDGENS are required as a secondary database involves two database: one for indexed database , the other for the secondary index databaseSlide32

Secondary Indexing Continued DBDGEN - The Secondary Index code for SRCS DB

DBD NAME=SRCS,ACCESS=(HIDAM,VSAM)

DSG1 DATASET DD1=DDSAT,DEVICE=3380,SIZE=4096,FRSPC=0,15) SEGM NAME=SRU,PARENT=0,BYTES=40 FIELD NAME=(SRUCD,SEQ,U),BYTES=2,START=1,TYPE=P …… SEGM NAME=EMPLY,PARENT=SRU,BYTES=80 LCHILD NAME= (MYPNTR,MYDBD),POINTER=INDX FIELD NAME=(EMPID,SEQ,U),BYTES=5,START=1,TYPE=P XDFLD NAME=MYINDX,SRCH=EMPID FIELD NAME=EMPNAME,BYTES=25,START=6,TYPE=C FIELD NAME=EMPPROJ,BYTES=15,START=31,TYPE=C FIELD NAME=EMPADDR,BYTES=35,START=46,TYPE=C ……. Slide33

Secondary Indexing Continued DBDGEN - The Secondary Index code for Secondary Index DBDBD NAME=MYIDBD,ACCESS=(INDEX)

DSG1 DATASET DD1=DDKAY,DEVICE=3380,SIZE=4096,FRSPC=0,15)

SEGM NAME=MYPNTR,PARENT=0,BYTES=6 LCHILD NAME= (EMPID,SRCS), INDX=MYINDX FIELD NAME=(MYEMPID,SEQ,U),BYTES=6,START=1,TYPE=CDBDGENFINISHENDPSB Requirements for Secondary Indexing. PCB TYPE=DB,DBDNAME=SRCS,KEYLEN=10,PROCOPT=LS, PROCSEQ=MYIDBD SENSEG NAME=EMPLY SENSEG NAME=SRU,PARENT=EMPLY PSBGEN PSBNAME=MYSBX,LANG=COBOL ENDSlide34

Difference Between MPP , BMP & DLI MPP (Message Processing Program) For Online programs( IMSDC) only. PSB used by a MPP program cannot be used by another programs simultaneously. Cannot run on Individual partitions.

BMP (Batch message processing) For batch programs only PSB used by a BMP program cannot be used by another programs simultaneously. All partitions specified in PSB will be allocated whether used by program or not. Cannot run on Individual partitions. DL/I It can be used as Interface between MPP and Database OR BMP and Database For batch DL/I job it can access database directly PSB of DL/I job can be used by another jobs simultaneously It can run on Individual partitions.