Information Management System

IMS

DatabasesWhat is a database?

A way of organizing data

Why database ?

• Increase data independence

• Increase data security

• Reduce data redundancy

• Maintain data integrity

TYPES OF DATABASES

• Hierarchical databases

• Network databases

• Relational databases

NETWORK MODEL

COMPANY CLUB

BUILDING VEHICLE PERSON

RELATIONAL MODELEMP TABLE

DEPT TABLE

EMPNO ADDR

LOCATION NO_OF_EMPL

DEPTNO NAME

DEPTNO

Hierarchical Model - Layout

I. Hospital general Info

A. Wards and Rooms in each Hospital

1. Patients in each Ward

a.Symptoms

b.Treatments

c.Doctors

B. Special Facilities in each Hospital

HIERARCHICAL MODELSegment Representation

S ym p tom Trea tm en t D oc to r

P a tien t

W ard F ac ility

H osp ita l

IMS DATABASE

• Information Management System.

• First and Oldest Database developed by IBM.

• DL/I user interface language

DL/I

OS Access methods

Appl. Program

OS Access methods

File or dataset

Appl. Program

Database

IMS Software Environment

IMS ENVIRONMENT

• IMS supports

– User written Batch Processing and Telecommunication applications.

– Provides Data Management Services and Data Communication Services.

• Data Management Services

– Support multiple applications using a common database.

• Data Communication Services

– Support multiple terminal-oriented applications using a common database.

Components of DB & DC 1. Application Program

• User written programs in COBOL, PL/I, Assembler

2. DB PCB

• Enables the program to communicate with DL/I to get information from database.

3. DL/I DATA LANGUAGE I

• Set of IMS program modules.

• Exists external to the application programs.

• Allows the application programs to access the database sequentially or randomly.

• Not a programming language.

APPLICATION PROGRAM

DB PCB

DL/I

IMSDATABASE

I/O PCB

IMS DC

TERMINAL

BATCH MODE PROCESS FLOW

Appl. Program

DB PCB

DL/I

IMS DB

ON-LINE MODE PROCESS FLOW

Terminal

IMS DC

I/O PCB

Appl. program.

DB PCB

DL/I

IMS DB

IMS DB

OS

DL/I

IMS Control Blocks

Appl Programs

IMS DC

IMS Software Environment

IMS ENVIRONMENT..• IMS database

– Center of the system. – Stored in direct access storage device (DASD).

• I/O PCB

- Enable program to communicate with IMS DC • IMS DC

– communicate with other programs and/or remote terminals.

• Terminal – Interactive on-line applications.

IMS Terminology

IMS - Terminology• Root

– Top most segment of the database– Does not have parent.

• Parent – Segment directly above

• Child – Segment directly below.

• Segment type – Generic term that describes collection of related data.

• Twins – All occurrences of a segment type under a single

parent.

– Can be more than two.

• Twin chain – Set of twins dependent on a particular parent

• Tree structure – No segment can have more than one parent.

• Segment– Smallest unit of information that can be retrieved.

– Maximum of 255 segments.

– Field

• An individual data item.

• Smallest unit of information in the database

– Dependent Segment

• Segments below a particular segment occurrence.

– Segment occurrence

• Collection of data items retrieved as a unit.

– Hierarchy chart

• Chart showing the relationship between segments.

– Database record

• a single occurrence of a root segment type and all its dependent segments

– Database

• Collection of root segment occurrences.

– Level

• Position of segment.

• Maximum 15 levels.

IMS HIERARCHIAL STRUCTURE

1

2

3

4

5

6

7

8

9

1011

12

13

14

15

1617

18

19

20

Employee1

Salary13

Salary12

Salary11

DeductY

DeductX

DeductW

DeductV

DeductU

AddressX3

AddressX2

AddressX1

Sequential Processing order 1) Top-to-bottom 2) Front-to-back 3) Left-to-right

1-11-X-Y-12-U-V-W-13-X1-X2-X3-2

Physical and Logical data structures

IMS ENVIRONMENT...

DEFINING THE DATABASE

• Define segments & hierarchical structure.

• Choose key and search fields.

• DBA communicates to IMS.

• Control block is created DBD.

• Coding a series of DBDGEN control statements.

• Consists of Assembler language macro statements.

DEFINING A LOGICAL DATA STRUCTURE

• Define logical data structure• PSB - Program specification block • PCB - Program communication block• PCB within one PSB defines one logical data

structure for a database • PSB generation (PSBGEN)• Application Data Structure(PCBs in PSB).

•LOOK IN CODING OF DBD.

•LOOK IN CODING OF PCB.

CODING OF DBD DBD NAME=EMPLOYEE,ACCESS=(HIDAM,OSAM)

DSGROUP0 DATASET DD1=DDEMP,DEVICE=3380,SIZE=(4096),FRSPC=(10,10)

SEGM NAME=EMPDATA,PARENT=0,BYTES=100

FIELD NAME=(EMPID,SEQ,U),BYTES=11,START=1,TYPE=C

SEGM NAME=WORKDATA,PARENT=EMPDATA,BYTES=200

FIELD NAME=(DEPTID,SEQ,U),BYTES=5,START=1,TYPE=C

DBDGEN

FINISH

END

CODING OF PCB

PCB TYPE=DB,DBDNAME=EMPDBD,KEYLEN=16

SENSEG NAME=EMPDATA,PARENT=0,PROCOPT=K

SENSEG NAME=WORKDATA,PARENT=EMPDATA,PROCOPT=G

PSBGEN LANG=COBOL,PSBNAME=EMPPSB1

END

EMPDATA

WORKDATA DEPDATA BENDATA

PCB TYPE=DB,DBDNAME=EMPDB,KEYLEN=16,PROCOPT=GSENSEG NAME=___________,PARENT=___________ SENSEG NAME=___________,PARENT=___________SENSEG NAME=___________,PARENT=___________ SENSEG NAME=___________,PARENT=___________ PSBGEN LANG=PLI,PSBNAME=EMPPSBYEND

IMS Call

AN IMS CALL

Five parts

• Call statement to DLI

• Function code

• PCB mask

• IO-AREA

• Segment Search Argument(s)

Call to DLI

CBLTDLI

• uses qualifications in form of SSAs

Other forms are

PLITDLI for PLI

ASMTDLI for assembly lang

EXECDLI

• uses where clause for search criteria

PCB MASK

How is PCB mask coded ?01 XXX- PCB-MASK.

05 XXX-DBD-NAME PIC X(08).

05 XXX-SEGMENT-LEVEL PIC XX.

05 XXX-STATUS-CODE PIC XX.

05 XXX-PROC-OPTS PIC X(04).

05 XXX-JCB-ADDRESS PIC S9(05) COMP.

05 XXX-SEG-NAME PIC X(08).

05 XXX-KEY-LENGTH PIC S9(05) COMP.

05 XXX-NUM-SENS-SEGS PIC S9(05) COMP.

05 XXX-KEY-FBK-AREA PIC X(??).

I/O AREA

• standard record description.

• holds database segments for manipulation.

• used by DL/I.

• can be used by the programmer.

• Area length.

SEGMENT SEARCH ARGUMENT

SEGMENT SEARCH ARGUMENT (SSA)

• identifies the segment which needs to be accessed

• SSA is an optional DL/I call parameter

• can also specify a particular segment type or segment occurrence

Types of SSAs

• Unqualified SSA

• Qualified SSA

SEGMENT SEARCH ARGUMENT..

UN QUALIFIED SSA

• only 8 byte segment name is specified

• 9th position of column is blank.

• does not indicate a particular occurrence of a segment.

• accesses the database sequentially.

Qualified SSA

•Searches for a specific occurrences of a segment.

•Has complete information about the segment occurrence

•supplies either key or search field in addition to segment name

RULES

• First field eight chars segment type

• 9th position identifies the type.

• When 9th position• ‘( ‘ indicates beginning of

qualification• ‘* ‘ SSA includes command

codes;qualification ‘(‘ follows command codes

• ‘)’ indicates end of qualification

SEGMENT SEARCH ARGUMENT

• QUALIFIED SSA EXAMPLE:

HOSPITAL(HOSPNAME =RIVEREDGE )

WARD (WARDNO = 02)

PATIENT (PATNAME =BROWN )

• UN QUALIFIED SSAEXAMPLE:

GU HOSPITAL

WARD

PATIENT

Operators in Qualified SSA

Equal to = EQ

Not equal to ¬= NE

Less than < LT

Less than or equal to <= =< LE

Greater than > GT

Greater than or equal to >= => GE

Function Codes

FUNCTION CODES

• Four byte-code.• Informs DL/I what to do in this call• 9 function codes

Function Codes

GU

•Get Unique.

•Unique occurrence of a segment.

GN

•Get-Next.

•Next occurrence of a segment.

GNP

•Get-Next-Within-Parent.

•Next occurrence of a segment under a parent.

•Retrieves child segments under a parent.

GHU

• Get-Hold-Unique.

GHN

• Get-Hold-Next.

GHNP

• Get-Hold-Next-within-Parent.

REPL

• REPLace.

• Replace an occurrence of a segment.

DLET

• DeLETe.

• Delete an occurrence of a segment.

ISRT

• InSeRT.

• Insert an occurrence of a segment.

DELETING, UPDATING, INSERTING SEGMENTS

• Rules for DELETING/UPDATING of segments• Issue Get-Hold call.

• No intervening calls(using the same database PCB MASK).

• No SSAs in the call.

• Do not modify the key field.

DELETE,REPLACE,INSERT CALLS

• SYNTAX TO DELETE

GHU HOSPITAL(HOSPNAME= MAC NEAL )

WARD (WARDNO = 01)

PATIENT (BEDIDENT=0003)

DLET

• SYNTAX TO REPLACE

GHU HOSPITAL(HOSPNAME=MAC NEAL )

WARD (WARDNO =04)

REPL

• SYNTAX TO INSERT

ISRT HOSPITAL(HOSPNAME=MAC NEAL ) WARD (WARDNO =04)

PATIENT

STATUS CODES

STATUS CODE

• DL/I call statement is executed a status code is generated.

• Code is based on the type of the call.

FOR GET-NEXT CALLS:

With Qualified SSAs.• Blank successful retrieval call.

• GE For segment not found.

Without SSAs.

• GA Moved up in level.

• GK New segment type encountered at same level.

• GB End of the database encountered.

FOR INSERT CALLS:

• II Segment already exists.

• IL Insert rule violation.

FOR INSERT STATUS CODES FOR LOADING CALLS:

• LB Segment already exists.

• LC Key value out of sequence.

• LD No parent for segment being loaded.

• LE Segment type out of sequence.

FOR DLET/REPL CALLS:

• DJ No previous GET-HOLD call.

• DA Key field modified.

• DX Delete rule violation.

• RX Replace rule violation.

Command Codes

COMMAND CODES

• Request a number of useful IMS functions.• used to save programming and processing time.• Number of SSAs reduced.• IMS to modify the way the call is handled. • There are ten command codes.

COMMAND CODES..

• D Put this segment into the I/O area (Path Call).

• N do not replace this segment.• C Concatenated key in SSA.• F Locate the first occurrence.• L Locate the last occurrence.• P Establish the Parentage at this level.• Q En-queue this segment .• U Maintain current position at this level.• V Maintain current position here and

higher level.

• -- Null command code.

COMMAND CODES

EXAMPLES:

• QUALIFIED SSAs WARD *D(WARDNO =04)

PATIENT *DNP(PATNAME =SMITH )

• UN QUALIFIED SSAs WARD *D

PATIENT *DN

COMMAND CODES..

D & N Command Code :

AIM : To print hospital and ward information for a patient and we also want to update the patient segment.

Without Command Codes

Step1: GU HOSPITAL(HOSPNAME =RIVEREDGE )

Step2: GN WARD (WARDNO =02)

Step3: GHU PATIENT(BEDIDENT =0003)

Step4: REPL

• With Command Codes

Step1: Hold call

GHU HOSPITAL*D(HOSPNAME =RIVEREDGE )

WARD *D(WARD =02)

PATIENT (BEDIDENT =0003)

Step 2: Replace call

REPL HOSPITAL*N(HOSPNAME =RIVEREDGE )

WARD *N(WARDNO =02)

PATIENT (BEDIDENT =0003)

COMMAND CODES...

Combination of D&N command codes

HOSPITAL*DN(HOSPNAME =RIVEREDGE )

WARD *DN(WARDNO =02)

PATIENT (BEDIDENT =0003)

Using C command code (Concatenation)

– With out command code

GHU HOSPITAL(HOSPNAME =RIVEREDGE )

WARD (WARDNO =02)

PATIENT (BEDIDENT =0003)

DOCTOR (DOCTNAME =BOSWELL )

– With command code

GHU DOCTOR *C(RIVEREDGE 020003BOSWELL )

A Simple Batch IMS COBOL Program

A COBOL-IMS application program structure

Working StorageI/O Areas ( Segments to and from Database)

Segment Search ArgumentsQualified or Unqualified

Linkage SectionPCB Area (Return information from DLI)

Procedure Division

Program Entry

Calls to DL/I (Get, Insert, Replace, Delete)

Processing Termination

DL/I Modules

DL/I Area

COBOL CODING USING IMS IDENTIFICATION DIVISION.

PROGRAM-ID.

ENVIRONMENT DIVISION.

*

DATA DIVISION.

*

01 INFILE.

03 HOSPNAME-IN PIC X(20).

03 WARDNO-IN PIC X(2).

03 PATIENT-IN PIC X(20).

*

WORKING-STORAGE SECTION.

77 GET-UNIQUE PIC XXXX VALUE ‘GU ‘.

01 HOSPITAL-SSA.

03 FILLER PIC X(19) VALUE ‘HOSPITAL(HOSPNAME =‘.

03 HOSPNAME-SSA PIC X(20).

03 FILLER PIC X VALUE ‘)’.

01 WARD-SSA.

03 FILLER PIC X(19) VALUE ‘WARD (WARDNO =‘.

03 WARDNO-SSA PIC X(2).

03 FILLER PIC X VALUE ‘)’.

COBOL CODING USING IMS..01 PATIENT-SSA.

03 FILLER PIC X(19) VALUE ‘PATIENT (PATNAME =‘.

03 PATNAME-SSA PIC X(20).

03 FILLER PIC X VALUE ‘)’.

01 IO-AREA COPY PATIENT.

LINKAGE SECTION.

01 PCB-MASK COPY MASKC.

PROCEDURE DIVISION.

ENTRY-LINKAGE.

ENTRY ‘DLITCBL’ USING PCB-MASK.

PROG-START.

OPEN INPUT INFILE.

OPEN OUTPUT OUTFILE.

READ-INPUT.

READ INFILE AT END GO TO END-OF-JOB.

MOVE HOSPNAME-IN TO HOSPNAME-SSA.

MOVE WARDNO-IN TO WARDNO-SSA.

MOVE PATNAME-IN TO PATNAME-SSA.

CALL ‘CBLIDLI’ USING GET-UNIQUE

PCB-MASK

IO-AREA

HOSPITAL-SSA

COBOL CODING USING IMS...

WARD-SSA

PATIENT-SSA.

IF STATUS-CODE EQUAL TO ‘GE’ OR ‘GB’

MOVE STATUS-CODE TO DUMP-AREA

MOVE ‘ PATIENT NOT FOUND’ TO PRINT-PATIENT-NAME

ELSE

IF STATUS CODE NOT = SPACES

DISPLAY ‘ ERROR IN DATABASE READ’ STATUS-CODE

CALL DUMP

END-IF

END-IF.

PERFORM PRINT-ROUTINE.

GO TO READ-INPUT.

PRINT-ROUTINE.

• ……………….

END-OF-JOB.

CLOSE INFILE.

CLOSE OUTFILE.

GOBACK.

COBOL CODING USING IMS...

01 HOSPITAL.

03 HOSPNAME PIC X(20).

03 HOSP-ADDR PIC X(30).

01 WARD.

03 WARDNO PIC XX.

03 BEDAVAIL PIC XXX.

01 PATIENT.

03 PATNAME PIC X(20).

03 PAT-ADDRESS PIC X(30).

01 SYMPTOM.

03 DIAG PIC X(20).

03 STMP-DATE PIC X(30).

01 TREATMENT.

03 TRTYPE PIC X(20).

03 TRDATE PIC X(10).

01 DOCTOR.

03 DOCNAME PIC X(20).

03 DOCADDRESS PIC X(30).

Multiple Positioning

Multiple Positioning

• Single Positioning

• Multi-Positioning

• Retrieving a set of child segments for each parent

Hospital database

S ym p tom Trea tm en t D oc to r

P a tien t

W ard F ac ility

H osp ita l

MULTI POSITIONING

GU HOSPITAL(HOSPNAME =XXX )

WARD (WARDNO = 01)

PATIENT (BEDIDENT =1012)

GNP SYMPTOM

GNP TREATMENT

GNP DOCTOR

SINGLE POSITIONING FAILS HERE..

GNP SYMPTOM

GNP TREATMENT

GNP DOCTOR

MULTI POSITIONING

PCB TYPE=DB,NAME=HOSPITAL, POS=M

• POS parameter • POS = M• POS =S• IMS maintains separate position within a data

record for each dependent segment type

Secondary Indexing

Secondary Indexing

• A self contained database

• stores a series of pointers to segments of database being indexed

• processing other than the key sequence

Secondary Indexing Terminology

• Index database

• PROCSEQ parameter

• Indexed field

• Index source segment

• Index target segment

• Index pointer segmentIndexed field + a pointer to target segment

A Secondary Index

HOSPITAL

WARD FACILITY

PATIENT

TREATMNTSYMPTOM DOCTOR

DIAGINDX

• Index target - Patient

• Index Source - Symptom

• Indexed fields - Diagnose+Prescription

• (XDIAG)

Using Secondary Index

PCB TYPE = DB, NAME=HOSPITAL

PROCOPT=A,PROCSEQ=DIAGINDX

1. GN HOSPITAL retrieves in DIAGNDX sequence

2. GU PATIENT(XDIAG =XXXX1231)

uses DIAGINDX to retrieve the required segment using the indexed field.

Using Secondary Index

SENSEG NAME=HOSPITAL,PARENT=0,INDICES=DIAGINDX

1. GN HOSPITAL

retreives the in normal sequence

2. GU PATIENT(XDIAG = xxxx1234 )

retreives using DIAGINDX with the index key.

Secondary Index Restrictions

• Any type of calls can be issued on segments below index target segment

• DLET or ISRT calls cannot be made for index target segment or any of its parents in original hierarchy

Independent-AND

• Can be used to retrieve data where more than one index pointer segment can point to a given index target segment.

GU PATIENT(XDIAG = PLAGUE * XDIAG = FLU )

GU PATIENT(XDIAG = PLAGUE # XDIAG = FLU )

Secondary IndexingA

B C

D

F

E

G

INDEX1

INDEX2

A

B

E

GPCB … PROCSEQ=INDEX1

PCB … PROCSEQ=INDEX2

Secondary Indexing Relationships

Secondary index and the database may have

• one to one relationshipIndex pointer segments have unique key fields

• one to many relationshipIndex pointers segments does not have the key field as

unique

Logical databases and Logical Relationships

Logical Relationships - A Snapshot

• Restructuring the hierarchy

• Connecting the physical databases

• Reduce redundancy of segments in different databases

Logical database terms

• Logical child

• Logical parent

• Logical database

• Logical Twins

An Example

HOSPITAL

WARD FACILITY

PATIENT

TREATMNTSYMPTOM DOCTOR Pointersegment

NAME

BILLING HISTORY

Logical Relationships - Types

• Unidirectional

• Bi-directional– bi-directional virtual logical relationship– bi-directional physical logical relationship

Logical databases

NAME

ADDRESS PAYROLL NAME

EXPR EDUC

SKILL

Payroll database (Physical) Skills database (Physical)

Logical databasesNAME SKILL

LOGICAL DBDGEN

NAMESKIL

MYPSB

2 physical databases

Are merged in to

Produce a logical dbd

The PCB (and program) use the name of the

logical database

Logical database

NAME

EXPR EDUC

SKILL

ADDRESS PAYROLL

Logical database

NAME

ADDRESS PAYROLL

EXPR EDUC

SKILL

Variable Length Segments

Variable Length Segments

• save space

• two byte length field

dataLength

1 2 3

Variable Length Segment

Variable Length Segment

SEGM NAME=TREATMENT, PARENT=PATIENT,BYTES=(160,90)

160 Maximum size of segment

90 Minimum size of segment

Generalized Sequential Access Method

GSAM

• Access to standard sequential dataset or VSAM ESDS using IMS calls

• no hierarchical structure

• no key or search fields

GSAM call

Call ‘CBLTDLI’ USING GET-NEXT

GSAM-PCB

I-O-AREA

GSAM-RSA.

DL/I Recovery & Restart Features

Terms for discussion

• Abnormal Termination routines

• IMS Log

• Recovery– forward recovery– backward recovery

Checkpointing

• Other terms -checkpoint,sync point, commit point, point of integrity

• Checkpoint call - CHKP

• Types of checkpointing• basic checkpointing

• symbolic checkpointing with extended restart facility

Basic CheckpointingLinkage Section.

01 I-O-PCB-MASK.

05 FILLER PIC X(10)

05 I-O-PCB-STATS-CODE PIC XX.

CALL ‘CBLTDLI’ USING DLI-CHKP

I-O-PCB-MASK

CHECKPOINT-ID

Symbolic CheckpointingWorking Storage Section.

01 COUNT-FIELDS

….

01 PRINT-FIELDS

…...

01 CHECKPOINT-ID PIC S9(08) COMP.

01 RESTART -WORK-AREA PIC X(12) VALUE SPACES.

01 LENGTH FIELDS COMP.

05 LENGTH-COUNT-FIELDS PIC S9(5) VALUE +11.

05 LENGTH-PRINT-FIELDS PIC S9(5) VALUE + 9.

05 LENGTH-LONGEST-SEGMENT PIC S9(5) VALUE + 128.

LINKAGE SECTION.

01 I-O-PCB.

05 FILLER PIC X(10).

05 I-O-PCB-STATUS-CODE PIC X(2).

…..

PROCEDURE DIVISION.

ENTRY ‘DLITCBL’ USING I-O-PCB ….

CALL ‘CBLTDLI” USING DLI-XRST

I-O-PCB

LENGTH-LONGEST-SEGMENT

RESTART-WORK-AREA

LENGTH-COUNT-FIELDS

COUNT-FIELDS

LENGTH-PRINT-FIELDS

PRINT-FIELDS.

IF I-O-PCB-STATUS-CODE NOT = SPACE

DISPLAY ‘RESTART-FAILED -- STATUS CODE :’ I-O-PCB-STATUS-CODE

ELSE

IF RESTART-WORK-AREA NOT= SPACES

PERFORM 100-REPOSITION-DATA-BASE.

……

230-ISSUE-CHECKPOINT-CALL.

ADD 1 TO CHECKPOINT-ID.

CALL ‘CBLTDLI’ USING DLI-CHKP

I-O-PCB

LENGTH-LONGEST-SEGMENT

CHEKPOINT-ID

LENGTH-COUNT-FIELDS

COUNT-FIELDS

LENGTH-PRINT-FIELDS

PRINT-FIELDS.

IF I-O-PCB-STATUS-CODE NOT =SPACE

DISPLAY ‘ CHECKPOINT FAILED -- STATUS CODE:’ I-O-PCB-STATUS-CODE

…..

General Structure of an Online Program

Get twa.

IF twa-save-area not = low values

****the control to this program has come from a different transaction

Get the some information from TWA

process the details from TWA

Load the map

send it and return.

else

if eibcalen > 0 (check commarea)

****the program is in pseudoconversation

get information from commarea

receive map

process the details on the map

send it and return

else

*****program is invoked for the first time from screen

Load the map with default values

send the map and return.