1. IMS - DB

2. SESSION 1 IMS GENERAL CONCEPTS
SESSION 2 DL/I CONTROL BLOCKS
SESSION 3 SEGMENT SEARCH ARGUMENTS (SSAs)
SESSION 4 COBOL BASICS FOR IMS
SESSION 5 DL/I CALLS
SESSION 6 COMMAND CODES
SESSION 7 DL/I CALLS EXERCISE
SESSION 8 DATABASE ACCESS METHODS
SESSION 9 MULTIPLE PROCESSING
SESSION 10 SECONDARY INDEXING
SESSION 11 LOGICAL RELATIONSHIP
SESSION 12 DB RECOVERY/RESTART
SESSION 13 EFFICIENT PROGRAMMING TIPS
SESSION 14 COMMON IMS ABENDS

3. SESSION 1
IMS GENERAL CONCEPTS

4. IMS GENERAL CONCEPTS IMS - INFORMATION MANAGEMENT SYSTEM
DEVELOPED IN 1968 BY IBM
DATA LANGUAGE-I (DL/I) WAS DEVELOPED AS A INTERFACE BETWEEN APPLICATION CODE AND DATA IN IMS DATABASE

5. IMS GENERAL CONCEPTS HIERARCHICAL STRUCTURE Continued ...
ROOT SEGMENT (PARENT)
FOLLOWS INVERTED TREE STRUCTURE
EACH BOX IN THE HIERARCHY REPRESENTS A SEGMENT
ROOT SEGMENT WILL BE ON TOP
EACH SEGMENT (EXCEPT ROOT SEGMENT) IS DIRECTLY DEPENDENT ON ONLY ONE SEGMENT A2
-- Level 1 A1
SEGMENT OCCURRNCES B3 B2 B1 C1 D1
-- Level 2
DEPENDENT SEGMENTS
TWIN SEGMENTS

6. IMS GENERAL CONCEPTS Continued ...
SEGMENT IS THE SMALLEST INFORMATION THAT DL/I CAN FETCH
EACH SEGMENT WILL HAVE UNIQUE 8 CHARACTER (MAX) NAME
SEGMENTS ARE MADE UP OF 1 OR MORE FIELDS
FIELD IS THE SMALLEST UNIT THAT DL/I CAN HANDLE
EACH FIELD WILL HAVE MAX 8 CHARACTER NAME
SEGMENT TYPE vs SEGMENT OCCURRENCE
SEGMENT OCCURRENCE IS A PARTICULAR INSTANCE OF A SEGMENT TYPE

7. IMS GENERAL CONCEPTS Continued ... TWO TYPES OF FIELDS KEY FIELDS
SEARCH FIELDS
KEY FIELD IS USED TO SEQUENCE DATABASE AND IT CAN NOT BE CHANGED
BOTH TYPES OF FIELDS CAN BE USED TO SEARCH DATABASE

8. IMS GENERAL CONCEPTS TYPES OF SEGMENTS Continued ... ROOT
A SEGMENT WITHOUT PARENT
PARENT
A SEGMENT WITH ONE OR MORE DEPENDENT SEGMENTS
DIRECTLY UNDER IT
CHILD
A SEGMENT WHICH IS DIRECTLY DEPENDENT ON ANOTHER
SEGMENT
DEPENDENT
ALL SEGMENTS UNDER A PARTICULAR SEGMENT OF THE
DATABASE
TWIN
ALL OCCURRENCES (2 OR MORE) OF A SEGMENT TYPE
UNDER A PARENT
SIBLINGS
OCCURRENCES OF DIFFERENT SEGMENT TYPES UNDER
A PARENT

9. IMS GENERAL CONCEPTS EXERCISE - 1 Continued ...2 3 4 5 6 7 8 9
1. WHICH SEGMENTS ARE DEPENDENT ON SEGMENT 4?
2. WHICH SEGMENTS ARE CHILD SEGMENTS OF SEGMENT 1?
3. WHICH SEGMENTS ARE DEPENDENT SEGMENTS OF SEGMENT 1?
4. HOW MANY LEVELS?
ANSWERS
1. SEGMENT 8 AND SEGMENT 9 ARE DEPENDENT OF SEGMENT 4
2. SEGMENTS 2, 3 & 4 ARE CHILD SEGMENTS
3. SEGMENTS 2, 3, 4, 5, 6, 7, 8, & 9 ARE DEPENDENTS
4. 3 LEVELS

10. IMS GENERAL CONCEPTS DATABASE RECORD Continued ...
ONE OCCURRENCE OF A ROOT SEGMENT ALONG WITH ALL ITS DEPENDENT SEGMENTS

11. HOW MANY DATABASE RECORDS?
IMS GENERAL CONCEPTS
Continued ...
EXERCISE-2
3 DATABASE RECORDS
HOW MANY DATABASE RECORDS?

12. IMS DATABASE LIMITATIONS
IMS GENERAL CONCEPTS
Continued ...
IMS DATABASE LIMITATIONS
IMS SUPPORTS
15 LEVELS
255 SEGMENTS
1000 FIELDS
NO LIMITATION ON NUMBER OF SEGMENT OCCURRENCES.

13. IMS GENERAL CONCEPTS IMS ENVIRONMENT Continued ...
DL/I FORMS BRIDGE BETWEEN APPLICATION PROGRAM AND IMS DATABASE
DL/I IS DATABASE MANAGER. IT CONSISTS OF IMS PROGRAM MODULES THAT RUN EXTERNAL TO APPLICATION PROGRAM
DL/I ALLOWS SEQUENTIAL OR RANDOM PROCESSING OF DATABASE
App Prog
DB PCB
interface
I/O PCB
interface
DL/I DC
Database
Terminal

14. IMS GENERAL CONCEPTS IMS ENVIRONMENT Continued ... MODES OF PROCESSING
BATCH DL/I MODE
MPP MODE
BMP MODE
ONLINE
BATCH
MPP
DL/I
BMP

15. IMS GENERAL CONCEPTS IMS ENVIRONMENT Continued ... BATCH DL/I
TRUE BATCH PROCESSING
NO DATA COMMUNICATION SERVICES ARE USED
DATABASES ACCESSED MUST BE OFFLINE
MPP (MESSAGE PROCESSING PROGRAM)
TRUE ONLINE PROCESSING
TRANSACTION ARE ENTERED AT TERMINAL AND STORED IN MESSAGE QUEUE
DATABASES ACCESSED MUST BE ONLINE

16. IMS GENERAL CONCEPTS IMS ENVIRONMENT Continued ...
BMP (BATCH MESSAGE PROCESSING)
TWO TYPES
1. TRANSACTION ORIENTED:
CAN READ & WRITE TO ONLINE MESSAGE QUEUES
CAN PROCESS ONLINE FILES AND DATABASES
2. BATCH ORIENTED:
CAN ONLY READ MESSAGE QUEUES
ACCESS ONLINE DATABASES IN BATCH MODE

17. SESSION 2
DL/I CONTROL BLOCKS

18. DL/I CONTROL BLOCKS DATABASE DESCRIPTION (DBD)
DEFINES THE LAYOUT OF THE DATABASE
DATABASE ADMINISTRATOR DEFINES LAYOUT USING DBDGEN MACRO
PROGRAM SPECIFICATION BLOCK (PSB)
DEFINES THE PROGRAMS VIEW OF THE DATABASE AND APPLICATION PROGRAMS ACCESS AUTHORITY TO DATABASE
DATABASE ADMINISTRATOR / PROGRAMMER DEFINES THIS USING PSBGEN MACRO

19. DATA BASE DESCRIPTION (DBD)
DL/I CONTROL BLOCKS
Continued ...
DATA BASE DESCRIPTION (DBD)
STATEMENTS IN DBD MACRO
STATEMENT
DESCRIPTION
DBD
SPECIFIES DATABASE NAME, ACCESS METHOD
DATASET
SPECIFIES DD NAME TO BE USED IN JCL, DISK TYPE
SEGM
SPECIFIES SEGMENT NAME,SEGMENT LENGTH, PARENT
FIELD
SPECIFIES FIELD NAME, LENGTH, STARTING POSITION
IDENTIFIES A FIELD AS KEY OR SEARCH FIELD

20. DL/I CONTROL BLOCKS SAMPLE DBDGEN Continued ... PRINT NOGEN
DBD NAME=VENDOR,ACCESS=HDAM
DATASET DD1=VEND,DEVICE=3380
SEGM NAME=VENSEG,PARENT=0,BYTES=10
FIELD NAME=(VENCODE,SEQ,U),BYTES=10,START=1,TYPE=C
SEGM NAME=ITEMSEG,PARENT=VENSEG,BYTES=5
FIELD NAME=(ITEMCODE,SEQ,U),BYTES=5,START=1,TYPE=C
SEGM NAME=LOCNSEG,PARENT=ITEMSEG,BYTES=9
FIELD NAME=(LOCNCODE,SEQ),BYTES=3,START=1,TYPE=C
FIELD NAME=ORDDATE,BYTES=6,START=4,TYPE=C
DBDGEN
FINISH
END

21. DATATYPES USED IN DBDGEN
DL/I CONTROL BLOCKS
Continued ...
DATATYPES USED IN DBDGEN
TYPE
DESCRIPTION
COBOL PICTURE C
Character (Default) X P
Packed Decimal
COMP-3 Z
Zoned Decimal S9 H
Half Word Binary
9(4) COMP F
Full Word Binary
9(8) COMP

22. DL/I CONTROL BLOCKS Continued ... CAN WE DEFINE OVERLAPPING FIELDS?
YES

23. PROGRAM SPECIFICATION BLOCK (PSB)
DL/I CONTROL BLOCKS
Continued ...
PROGRAM SPECIFICATION BLOCK (PSB)
MADE UP OF ONE OR MORE PROGRAM COMMUNICATION BLOCKS (PCBs)
DB PCB - DEFINES PROGRAM’S VIEW OF A IMS DATABASE
WHENEVER A DATABASE VIEW DEFINED BY THE PCB IS ACCESSED BY A CALL, THE RESULTS OF CALL ARE PASSED THROUGH THE PCB TO PROGRAM
PSB IS GENERATED BY PSBGEN MACRO

24. DL/I CONTROL BLOCKS Continued ... PCB GIVES LOGICAL VIEW OF A DATABASE
PORTION OF DATABASE THAT THE PROGRAM PROCESSES IS CALLED APPLICATION DATA STRUCTURE
DATABASE
PCB A A B C C D E E

25. DL/I CONTROL BLOCKS SAMPLE PSBGEN Continued ... PRINT NOGEN
PCB TYPE=DB,DBDNAME=VENDOR,KEYLEN=15,PROCOPT=LS
SENSEG NAME=VENSEG
SENSEG NAME=ITEMSEG,PARENT=VENSEG
PSBGEN
END
KEYLEN IS THE LENGTH OF CONCATENATED KEY

26. DL/I CONTROL BLOCKS Continued ...
PROCOPTS IN PSB DEFINES SECURITY LEVEL FOR THE PROGRAM
PROCOPT
DESCRIPTION G
Get or Read I
Insert R
Replace D
Delete A
All Options (G, I, R, D) L
Initial Load LS
Sequential Initial Load K
Access only Key of segment O
Used with G to Indicate that Hold is not allowed P
Path Calls

27. DL/I CONTROL BLOCKS Continued ...
APPLICATION PROGRAM CAN HAVE MULTIPLE VIEWS OF A DATABASE BY USING SEPARATE PCBS FOR A SINGLE DATABASE
PSB
PCB1
PCB2
PCB3
PCB4
DBD1
DBD2
DBD3

28. DL/I CONTROL BLOCKS Continued ... PRINT NOGEN
PCB TYPE=DB,DBDNAME=VENDOR,KEYLEN=15
SENSEG NAME=VENSEG,PROCOPT=G
SENSEG NAME=ITEMSEG,PARENT=VENSEG,PROCOPT=R
SENSEG NAME=LOCNSEG,PARENT=ITEMSEG,PROCOPT=A
PSBGEN
END
1. ITEMSEG AND LOCNSEG CAN BE UPDATED
2. VENSEG CAN NOT BE UPDATED AS THE PROCOPT IS JUST READ (G)
3. GIR
1. LIST THE SEGMENTS THAT MAY BE UPDATED USING THIS PSB
2. LIST THE SEGMENTS THAT CANNOT BE UPDATED
3. GIVE THE VALID PROCOPT TO BE CODED FOR ADDING AND REPLACING RECORDS IN LOCATION SEGMENT

29. DL/I CONTROL BLOCKS
Continued ...
EMPDATA
WORKDATA
DEPTDATA
BENDATA
BASED ON THE ABOVE VIEW OF DATABASE FILL IN THE MISSING PIECES
OF PCB
PCB TYPE=DB,DBDNAME=EMPDB,KEYLEN=16,PROCOPT=G
SENSEG NAME=_________________,PARENT=_____________________
PSBGEN LANG=COBOL,PSBNAME=EMPPSBY
END
SENESG NAME=EMPDATA,PARENT=0
SENSEG NAME=WORKDATA,PARENT=EMPDATA
SENSEG NAME=DEPTDATA,NAME=EMPDATA
SENSEG NAME=BENDATA,NAME=EMPDATA

30. SEGMENT SEARCH ARGUMENT
SESSION 3
SEGMENT SEARCH ARGUMENT

31. SEGMENT SEARCH ARGUMENT
THE SSA IS AN AREA IN WORKING STORAGE USED TO IDENTIFY THE SEGMENT TO WHICH ACCESS IS REQUIRED
IT IS AN OPTIONAL DL/I CALL PARAMETER THAT QUALIFIES A CALL BY SPECIFIYING A PARTICULAR SEGMENT TYPE OR OCCURRENCE
WHEN SPECIFIED IN A DL/I CALL
THE SSA ALWAYS FOLLOWS I/O PARAMETER
THERE MAY BE 1 TO 15 SSAs IN A CALL STATEMENT
THE SSAs MUST APPEAR IN HIERARCHICAL ORDER BY SEGMENT TYPE
THE SSA CONTAINS INFORMATION TO OBTAIN THE REQUIRED SEGMENT. THE INFORMATION COULD BY SEGMENT NAME OR SEGMENT NAME & SEGMENT KEY OR SEGMENT NAME & SEARCH FIELD

32. SEGMENT SEARCH ARGUMENT WHAT IS THE SIGNIFICANCE OF MAX 15 SSA?
Continued ...
SEGMENT SEARCH ARGUMENT
WHAT IS THE SIGNIFICANCE OF MAX 15 SSA?
YOU CAN HAVE 1 SSA FOR EACH LEVEL OF HIERARCHY. SINCE IMS HAS A LIMITATION OF 15 LEVELS AS MAXIMUM, WE CAN HAVE MAXIMUM OF 15 SSAS

33. SEGMENT SEARCH ARGUMENT
Continued ...
SEGMENT SEARCH ARGUMENT
TYPES OF SSAS
UNQUALIFIED
SEARCHES FOR A SPECIFIC SEGMENT TYPE
QUALIFIED
SEARCHES FOR A SPECIFIC SEGMENT OCCURRENCE
MORE EFFICIENT THAN UNQUALIFIED SSA

34. SEGMENT SEARCH ARGUMENT
Continued ...
SEGMENT SEARCH ARGUMENT
UNQUALIFIED SSA
WORKING-STORAGE-SECTION.
…………..
01 HISTORY-SSA.
05 SEGMENT-NAME PIC X(8) VALUE ‘HISTORY ‘.
05 FILLER PIC X(1) VALUE SPACE.
Blank in 9th position or ‘*’ in 9th position ‘-‘ in position 10 and a blank in position 11 H I S T O R Y H I S T O R Y * -

35. SEGMENT SEARCH ARGUMENT
Continued ...
SEGMENT SEARCH ARGUMENT
QUALIFIED SSA
WORKING-STORAGE-SECTION.
…………..
01 SSA-EMPLOYEE.
03 SEGMENT-NAME PIC X(8) VALUE ‘EMPLOYEE’
03 COMMAND-CODE PIC X(2) VALUE ‘*-’.
03 BEGIN-QUALIFY PIC X(1) VALUE ‘(‘.
03 KEY-NAME PIC X(8) VALUE ‘EMPKEY ‘.
03 OPERATOR PIC X(2) VALUE ‘ =‘.
03 KEY-VALUE PIC X(12) .
03 END-QUALIFY PIC X(1) VALUE ‘)‘.
PROCEDURE DIVISION.
…..
MOVE ‘ ’ TO KEY-VALUE.
CALL ‘CBLTDLI’ USING FUNC-CODE, PCB-MASK-1, IO-AREA, SSA-EMPLOYEE.

36. SEGMENT SEARCH ARGUMENT
Continued ...
SEGMENT SEARCH ARGUMENT
OPERATORS USED IN QUALIFIED SSA
OPERATOR
SYMBOLS
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’, ‘>=‘, ‘=>’

37. SEGMENT SEARCH ARGUMENT
Continued ...
SEGMENT SEARCH ARGUMENT
COMMAND CODES
COMMAND CODES INCREASE THE FUNCTIONALITY OF IMS CALLS
COMMAND CODES ARE DESIGNATED BY AN ASTERISK ‘*’ FOLLOWED BY CHARACTERS
NOTE: Detailed description of Command codes will be covered in Session “COMMAND CODES”

38. SESSION 4
COBOL BASICS FOR IMS

39. COBOL BASICS FOR IMS DATA DIVISION
IN A COBOL-IMS PROGRAM. THE FIRST SECTION TO CONTAIN ANY IMS RELATED
COMPONENTS IS THE WORKING STORAGE SECTION
IDENTIFICATION DIVISION
ENVIRONMENT DIVISION
DATA DIVISION
FILE SECTION
WORKING STORAGE SECTION
LINKAGE SECTION
PROCEDURE DIVISION
FUNCTION CODES
I/O AREA
SEGMENT SEARCH ARGUMENTS
PCB MASKS

40. COBOL BASICS FOR IMS FUNCTION CODES Continued ...
A FUNCTION CODE IS A 4 BYTE CODE TO TELL DL/I WHAT KIND OF CALL THE PROGRAM IS MAKING
SOME VALID FUNCTION CODES ARE
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
DLET - DELETE
REPL - REPLACE
ISRT - INSERT
XRST - EXTENDED RESTART
CHKP - CHECKPOINT

41. COBOL BASICS FOR IMS INPUT/OUTPUT AREA Continued ...
IS A STANDARD RECORD DESCRIPTION IN THE WORKING STORAGE SECTION WHICH HOLDS DATABASE SEGMENTS FOR MANIPULATION
IS USED BY DL/I TO PASS SEGMENTS TO THE PROGRAM
CAN BE USED BY PROGRAMMER TO ADD OR REPLACE SEGMENT DATA
MUST BE EQUAL TO OR GREATER THAN THE LENGTH OF THE LONGEST SEGMENT TO BE USED BY THE PROGRAM
IN CASES WHERE MULTIPLE SEGMENTS OF A HIERARCHY ARE UPDATED OR RETRIEVED, THE I/O AREA MUST BE LARGE ENOUGH TO HOLD THE LARGEST CONCATENATION OF THESE SEGMENTS

42. COBOL BASICS FOR IMS THE PCB MASK Continued ...
USED IN LINKAGE SECTION
LINKAGE SECTION
01 DB-PCB-1.
03 DBD-NAME PIC X(8).
03 SEG-LEVEL PIC X(2).
03 STATUS-CODE PIC X(2).
03 PROC-OPTIONS PIC X(4).
03 IMS-RESERVED PIC S9(5) COMP.
03 SEG-NAME PIC X(8).
03 KEY-LEN PIC S9(5) COMP.
03 NUM-SENS-SEGS PIC S9(5) COMP.
03 KEY-FEEDBACK PIC X(??). <= length depends on segment key

43. COBOL BASICS FOR IMS THE PCB MASK Continued ...
THERE SHOULD BE ATLEAST ONE PCB FOR EACH DATABASE USED
STATUS CODE OF PCB MASK EXPLAINS WHETHER A CALL IS SUCCESSFUL OR NOT
THE SEQUENCE IN WHICH PCB MASKS ARE DEFINED IN LINKAGE SECTION NEED NOT BE SAME AS THAT IN PSBGEN MACRO

44. COBOL BASICS FOR IMS PROCEDURE DIVISION Continued ...
ENTRY ‘DLITCBL’ USING DB-PCB-1, DB-PCB-2. <= Sequence should match that of
:::::::::::: PSB Macro
::::::::::::
CALL ‘CBLTDLI’ USING WS-PARM-COUNT, <= Optional
WS-FUNCTION-CODE,
DB-PCB-MASK,
IO-AREA,
SSA-1, SSA-2, SSA-3, ….
::::::::::
GOBACK.

45. COBOL BASICS FOR IMS Continued ...
RUN JCL EXECUTES THE BATCH PROCESSOR DFSRRC00 AND PASSES THE APPLICATION PROGRAM NAME AND PSBNAME AS PARAMETERS
ENTRY DLITCBL PASSES THE PCB ADDRESS TO THE PROGRAM
CBLTDLI ACCEPTS PARAMETERS LIKE FUNCTION CODE, I/O AREA AND SSA TO DO THE NECESSARY DATABASE OPERATIONS AND RETURNS DATA AND STATUS CODES DESCRIBING THE SUCCESS OF THE CALL
GOBACK IN THE COBOL PROGRAM TAKES THE CONTROL BACKTO DL/I WHICH PERFORMS IMS FILES CLOSING AND TERMINATES THE BATCH STEP. “STOP RUN” SHOULD NEVER BE USED AS IT WILL NOT FREE RESOURCES
RUN JCL
PROGRAM NAME
PSB NAME
DL/I
IMS
DATABASE
DLITCBL
CBLTDLI
GOBACK
APPLICATION
PROGRAM

46. SESSION 5
DL/I CALLS

47. DL/I CALLS DL/I RETRIEVAL CALLS
ONE OF THE FOLLOWING FUNCTIONS WILL BE USED IN A RETRIEVAL DL/I CALL
GU - GET UNIQUE
GN - GET NEXT
GNP - GET NEXT WITHIN PARENT
WHEN A RETRIEVAL IS DONE WITH AN INTENT TO UPDATE OR DELETE RECORDS, THE ABOVE FUNCTION CODES WILL BE PREFIXED WITH ‘HOLD’
GHU - GET HOLD UNIQUE
GHN - GET HOLD NEXT
GHNP - GET HOLD NEXT WITHIN PARENT

48. DL/I CALLS GET UNIQUE EXERCISE: WRITE A GU TO RETRIEVE FKEY=10
Continued ...
DL/I CALLS
GET UNIQUE
CALL ‘CBLTDLI’ USING ‘GU ‘, PCB-MASK,
SEGMENT-IO-AREA
SEGMENTA*-(AKEY=1)
SEGMENTB*-(BKEY=2)
SEGMENTD*-(DKEY=6)
AFTER THE CALL SEGMENTD WITH DKEY=6 WILL BE IN SEGMENT-IO-AREA 1
AKEY
EKEY 11 7
BKEY 2 8
CALL ‘CBLTDLI’ USING ‘GU ‘, PCB-MASK, SEGMENT-IO-AREA,
SEGMENTA*-(AKEY=1)
SEGMENTE*-(EKEY=8)
SEGMENTF*-(FKEY=10) 6 4 10 3 5 9
CKEY
DKEY
FKEY
EXERCISE: WRITE A GU TO RETRIEVE FKEY=10

49. WHAT WILL BE THE OUTPUT OF A GU CALL WITH NO SSA?
Continued ...
DL/I CALLS
WHAT WILL BE THE OUTPUT OF A GU CALL WITH NO SSA?
THE FIRST ROOT SEGMENT OCCURRENCE OF THE DATABASE WILL BE RETRIEVED IN SEGMENT I/O AREA

50. DL/I CALLS GET NEXT Continued ... RETREIVAL SEQUENCE TOP TO BOTTOM
FRONT TO BACK
LEFT TO RIGHT
AKEY 1 11 7
EKEY 2 8
BKEY GA 6 4 10 3 5 9 GK
DKEY
FKEY
CKEY

51. AFTER THE CALL SEGMENTE WITH EKEY=8 WILL BE IN PROGRAM I/O AREA
Continued ...
DL/I CALLS
CALL ‘CBLTDLI’ USING ‘GN ‘, PCB-MASK,
SEG-IO-AREA,
SEGMENTA*-(AKEY=1)
SEGMENTE*-(EKEY=8)
AFTER THE CALL SEGMENTE WITH EKEY=8 WILL BE IN PROGRAM I/O AREA 1
AKEY 7 11
EKEY 2 8
BKEY
YOU WILL GET END OF DATABASE STATUS CODE “GB” 6 4 10 3 5 9
FKEY
DKEY
CKEY
EXERCISE: WHAT WILL BE THE RESULTS OF FOUR CONSEQUETIVE GNs AFTER EKEY=8 IS RETRIEVED

52. DL/I CALLS GET NEXT WITHIN PARENT Continued ...
CALL ‘CBLTDLI’ USING ‘GN ’, LS-PCB-MASK, SEGMENT-IO-AREA,
SEGMENTA*-(AKEY=1)
SEGMENTB*-(BKEY=2)
CALL ‘CBLTDLI’ USING ‘GNP ‘, LS-PCB-MASK, SEGMENT-IO-AREA
AFTER THE CALL SEGMENTC WITH CKEY=3 WILL BE IN SEGMENT-IO-AREA
AKEY 1 11 7
EKEY 2 8
BKEY 6 4 10 3 5 9
DKEY
CKEY
FKEY

53. Continued ...
DL/I CALLS
WHAT WILL BE THE OUTPUT IF GNP IS DONE 4 MORE TIMES IN
PREVIOUS EXAMPLE?
WHEN THERE ARE NO MORE SEGMENTS WITHIN THE ESTABLISHED PARENTAGE, DL/I RETURNS A STATUS CODE OF ‘GE’.
SO YOU WILL NEVER GET ‘GB’ STATUS CODE WITH GNP CALLS

54. DL/I CALLS PATH CALLS EXERCISE Continued ...
CALL ‘CBLTDLI’ USING ‘GN ‘, LS-PCB-MASK, WS-SEG-IO-AREA,
SEGMENTA*D(AKEY=1)
SEGMENTF*-(FKEY=10)
WHAT WILL BE THE RESULT AFTER SUCCESSFUL COMPLETION OF THE ABOVE CALL? 1 11 7
EKEY 2 8
BKEY
DL/I WILL ASSUME UNQUALIFIED SSA FOR MISSING SEGMENTS IN THE HIERARCHY DURING RETRIEVE CALL. ONLY SEGMENTS 1 AND 10 WILL BE RETRIEVED INTO I/O AREA.
WARNING: UNQUALIFIED CALLS ARE INEFFICIENT. 6 4 10 3 5 9
DKEY
CKEY
FKEY

55. GET HOLD CALLS (GHU/GHN/GHNP)
Continued ...
DL/I CALLS
GET HOLD CALLS (GHU/GHN/GHNP)
FUNCTIONS IDENTICAL TO GU/GN/GNP
INDICATES THE REQUESTED SEGMENT(S) MAY BE DELETED OR REPLACED FORCING IMS TO PUT A LOCK ON THESE SEGMENTS WHICH WILL BE RELEASED ONLY AFTER ANOTHER CALL BY SAME PCB
THIS ENSURES DATA INTEGRITY

56. DL/I CALLS DELETE/REPLACE CALLS Continued ...
MUST HAVE BEEN OBTAINED WITH A GET HOLD CALL (GHU, GHN, GHNP)
NO INTERVENING CALLS BETWEEN GET HOLD CALL AND REPLACE/DELETE CALLS
MULTIPLE REPLACE ALLOWED AFTER GET HOLD

57. WHAT WILL BE THE RESULT IF THE FIRST GHU CALL IS SEGMENTA*D(AKEY=1)?
Continued ...
DL/I CALLS
DELETE CALL
CALL ‘CBLTDLI’ USING ‘GHU ‘, LS-PCB-MASK, WS-SEGMENT-IO-AREA
SEGMENTA*-(AKEY=1)
SEGMENTB*-(BKEY=2)
CALL ‘CBLTDLI’ USING ‘DLET’, LS-PCB-MASK 1 11 7
EKEY 2 8
BKEY
SEGMENT 1 AND ALL ITS DEPENDENTS WILL BE DELETED 6 4 10 3 5 9
DKEY
CKEY
WHAT WILL BE THE RESULT IF THE FIRST GHU CALL IS SEGMENTA*D(AKEY=1)?

58. DL/I CALLS REPLACE (REPL) Continued ... UPDATE CONTENTS OF A SEGMENT
KEY FIELD MAY NOT BE ALTERED
SSAs ARE NOT USED NORMALLY
COMMAND CODES
D - TO REPLACE PATH OF SEGMENTS
N - TO EXCLUDE SEGMENTS FROM PATH
STATUS CODES
DA - TRYING TO CHANGE KEY
DJ - NO PRECEDING GET HOLD CALL
RX - REPLACE RULE VIOLATION

59. Continued ...
DL/I CALLS
CALL ‘CBLTDLI’ USING ‘GHU ‘, LS-PCB-MASK, WS-IO-AREA,
SEGMENTA*-(AKEY=1)
SEGMENTB*-(BKEY=2)
SEGMENTC*-(CKEY=3)
Change contents of WS-IO-AREA
CALL ‘CBLTDLI USING ‘REPL’, LS-PCB-MASK, WS-IO-AREA
WILL RESULT IN UPDATE OF SEGMENTC 1 11 7
EKEY 2 8
BKEY 6 4 10 3 5 9
DKEY
CKEY
FKEY

60. DL/I CALLS INSERT (ISRT) Continued ... TWO MODES OF INSERT
LOAD MODE - FOR INITIAL LOADING OF DATABASE
UPDATE MODE - ADD TO EXISTING DATABASE
LOAD MODE:
FOR LOAD MODE PROCOPT = L or LS MUST BE SPECIFIED IN PSB
PROCOPT=L LOADS DATABASE BUT NOT NECESSARILY IN SEQUENTIAL ORDER

61. DL/I CALLS INSERT (ISRT) Continued ... UPDATE MODE:
FOR UPDATE MODE PROCOPT=I or IS MUST BE SPECIFIED IN PSB
PROCOPT=I INSERTS SEGMENTS IN SEQ OR RANDOM ORDER
PROCOPT=IS ADDS NEW SEGMENTS ONLY IN ASCENDING ORDER
COMMAND CODES
“F” OR “L” - OVERRIDES INSERT RULE
“D” - INSERT PATH OF SEGMENTS

62. Continued ...
DL/I CALLS
MOVE DATA FOR SEGMENTE INTO WS-SEGMENT-IO-AREA WITH EKEY=99
CALL ‘CBLTDLI’ USING ‘ISRT’, LS-PCB-MASK, WS-SEGMENT-IO-AREA,
SEGMENTA*-(AKEY=1)
SEGMENTE
AFTER THE CALL SEGMENTE WITH EKEY=99 IS INSERTED 1 99 11 7
EKEY 2 8
BKEY 6 4 10 3 5 9
DKEY
CKEY
FKEY

63. SOME COMMON STATUS CODES
Continued ...
DL/I CALLS
SOME COMMON STATUS CODES
STATUS CODE
DESCRIPTION
CALL TYPES
SPACES
SUCCESSFUL CALL
ALL CALLS AC
CALL HAS SSA WITH A HIERARCHICAL ERROR
ALL GET CALLS
ISRT AI
ERROR WHILE OPENING DATABASE. COMMON CAUSE IS LOADING A DATABASE WHICH IS NOT EMPTY OR DO OTHER THAN LOAD PROCESSING ON EMPTY DATABASE
ALL CALLS AJ
CALL SPECIFIES AN INVALID SSA
ALL CALLS AK
FIELD NAMED IN A QUALIFIED SSA IS NOT CORRECT
ALL GET CALLS
ISRT DA
SEQUENCE FIELD IS CHANGED
REPL
CALL ‘CBLTDLI’ USING ‘GU ‘, PCB-MASK, SEGMENT-IO-AREA,
SEGMENTA*-(AKEY=1)
SEGMENTE*-(EKEY=8)
SEGMENTF*-(FKEY=10) DJ
CALL IS NOT PRECEDED BY A SUCCESSFUL GET HOLD CALL
DLET
REPL GA
A HIGHER LEVEL SEGMENT IS RETRIEVED IN SEQUENTIAL PROCESSING
GN, GNP

64. SOME COMMON STATUS CODES
Continued ...
DL/I CALLS
SOME COMMON STATUS CODES
STATUS CODE
DESCRIPTION
CALL TYPES GB
END OF DATA BASE WAS REACHED DURING SEQUENTIAL RETRIEVAL GN GE
SPECIFIED SEGMENT NOT FOUND
ALL GET CALLS
ISRT GK
A SEGMENT OF DIFFERENT TYPE, BUT AT THE SAME LEVEL IS RETRIEVED DURING SEQUENTIAL PROCESSING
GN, GNP GP
PROPER PARENTAGE IS NOT IN EFFECT
GNP II
DUPLICATE INSERT
ISRT
CALL ‘CBLTDLI’ USING ‘GU ‘, PCB-MASK, SEGMENT-IO-AREA,
SEGMENTA*-(AKEY=1)
SEGMENTE*-(EKEY=8)
SEGMENTF*-(FKEY=10)

65. SESSION 6
COMMAND CODES

66. H I S T O R Y * - COMMAND CODES
ONE OR MORE COMMAND CODES CAN BE USED IN SSA
EACH COMMAND CODE IS REPRESENTED BY A SINGLE CHARACTER FOLLOWING AN ASTERISK AFTER SEGMENT NAME H I S T O R Y * -
DL/I CONSIDERS ALL CHARACTERS FOLLOWING ‘*’ TO BE COMMAND CODES TILL IT ENCOUNTERS A BLANK OR ‘(‘
RESULTS IN MINIMIZING THE NUMBER OF CALLS AND HENCE IMPROVE PROGRAM EFFICIENCY

67. COMMAND CODES SOME COMMAND CODES Continued ... COMMAND CODE
DESCRIPTION D
RETRIEVE A PATH F
FIRST OCCURRENCE OF SEGMENT TYPE L
LAST OCCURRENCE OF SEGMENT TYPE U
MAINTAIN CURRENT POSITION AT THIS LEVEL V
MAINTAIN CURRENT POSITION AT THIS AND HIGHER LEVELS N
DO NOT REPLACE THIS SEGMENT C
USE A CONCATENATED KEY P
ESTABLISH PARENTAGE AT THIS LEVEL -
NULL/IGNORE

68. COMMAND CODES COMMAND CODE “D” Continued ...
REQUESTS DL/I TO USE PATH CALLS
ALLOWS ENTIRE PATH IN SEGMENT HIERARCHY TO BE RETRIEVED IN ONE SINGLE CALL
FOR PROGRAMS USING PATH CALLS PROCOPT IN PSB SHOULD HAVE “P” AS ONE OF THE VALUES
DL/I DOES NOT RETRIEVE SEGMENTS IF THE CORRESPONDING SSA DOES NOT HAVE PATH COMMAND CODE “D”

69. COMMAND CODES COMMAND CODE “D” Continued ...
SEGMENT IN THE LAST SSA WILL ALWAYS BE RETRIEVED EVEN IF SSA DOES NOT HAVE COMMAND CODE “D”
FOR ISRT CALLS COMMAND CODE “D” DESIGNATES THE FIRST SEGMENT TO BE INSERTED
FOR ISRT CALLS SSAS FOR LOWER LEVEL SEGMENTS NEED NOT HAVE “D” COMMAND CODE, “D” COMMAND CODE IS PROPAGATED TO ALL SPECIFIED SEGMENTS AUTOMATICALLY
I/O AREA USED SHOULD BE BIG ENOUGH TO ACCOMMODATE ALL SEGMENTS IN PATH

70. COMMAND CODES PATH CALLS EXAMPLE Continued ...
CALL ‘CBLTDLI’ USING ‘GN ‘, LS-PCB-MASK, WS-SEG-IO-AREA, SEGMENTA*D(AKEY=1)
SEGMENTB*D(BKEY=2)
SEGMENTD*-(DKEY=5)
AFTER THE CALL SEGMENTS #1, #2 & #5 WILL BE RETURNED IN I/O AREA
AKEY 1 11 7
EKEY 2 8
BKEY 6 4 10 3 5 9
DKEY
CKEY
FKEY

71. COMMAND CODES COMMAND CODE “F” Continued ...
CALL PROCESSES FIRST OCCURRENCE OF THE SEGMENT TYPE
EXAMPLE:
SEGMENT 2 CAN BE RETRIEVED AFTER SEGMENT 4 BY USING
CALL ‘CBLTDLI’ USING ‘GNP ‘ LS-PCB-MASK, WS-SEG-IO-AREA,
SEGMENTB*F 1
SEGMENTA 4 2 3
SEGMENTC
SEGMENTB

72. COMMAND CODES COMMAND CODE “L” Continued ...
CALL PROCESSES LAST OCCURRENCE OF THE SEGMENT TYPE
EXAMPLE:
SEGMENT 4 CAN BE RETRIEVED AFTER SEGMENT 2 BY USING
CALL ‘CBLTDLI’ USING ‘GNP ‘ LS-PCB-MASK, WS-SEG-IO-AREA,
SEGMENTC*L 1
SEGMENTA 4 2 3
SEGMENTC
SEGMENTB

73. COMMAND CODES COMMAND CODE “N” Continued ...
USED IN REPL CALLS FOLLOWING PATH CALLS
IF ANY SEGMENT RETRIEVED DURING PATH CALL NEED NOT BE REPLACED COMMAND CODE “N” IS USED IN SSA OF THAT SEGMENT

74. COMMAND CODES COMMAND CODE “P” Continued ...
IS USED TO SET PARENTAGE TO A SPECIFIC SEGMENT IN THE HIERARCHY USED IN SSAS
EXAMPLE:
CALL ‘CBLTDLI’ USING ‘GU ‘ LS-PCB-MASK, WS-IO-AREA
SEGMENTA*P
SEGMENTC
WILL RETRIEVE SEGMENTC TO I/O AREA BUT PARENTAGE WILL BE SET TO SEGMENTA 1
SEGMENTA 2 3
SEGMENTC
SEGMENTB

75. SESSION 7
DL/I CALL EXERCISE

76. DL/I CALL EXERCISE Continued ... COURSE COURSE# TITLE DESCRIPN PREREQ
OFFERING
COURSE#
TITLE
DATE
LOCATION
FORMAT
TEACHER
STUDENT
EMPNUM
NAME
EMPNUM
NAME
GRADE

77. DL/I CALL EXERCISE Continued ...
GIVE SYNTAX OF DL/I CALLS FOR THE FOLLOWING SCENARIOS
1. GET THE FIRST OFFERING OCCURRENCE WHERE THE LOCATION IS “CHENNAI”
2. GET ALL STUDENT OCCURENCES FOR THE OFFERING FOUND IN 1
3. GET ONLY STUDENT OCCURENCES WITH GRADE OF “A”
4. SEQUENTIAL READ OF ALL SEGMENTS IN THE DATABASE
1. GU COURSE
OFFERING (LOCATION=‘CHENNAI’)
2. GU COURSE
DO WHILE STATUS-CODE = ‘ ‘
GNP STUDENT
END-DO
3. GU COURSE
GNP STUDENT (GRADE=‘A’)
4. GU COURSE GN

78. DL/I CALL EXERCISE Continued ...
5. GET ALL STUDENTS WITH GRADE OF “A” IN COURSE “IMS”
6. ADD A STUDENT OCCURRENCE FOR THE COURSE “IMS” OFFERED ON DATE “3/26/02”
7. DELETE THE OFFERING OF COURSE “XYZ” ON 26 March, 2002
8. CHANGE THE LOCATION OF COURSE “IMS” OFFERED ON “3/26/02” TO “MUMBAI”
5. GU COURSE (TITLE=‘IMS’)
DO WHILE STATUS-CODE = ‘ ‘
GNP STUDENT (GRADE=“A”)
END-DO
6. Build STUDENT segment in I/O area
ISRT COURSE (TITLE=‘IMS’)
OFFERING (DATE=‘032602’)
STUDENT
7. GHU COURSE (TITLE=‘XYZ’)
DLET
8. GHU COURSE (TITLE=‘IMS’)
change the location name from ‘CHENNAI’ to ‘MUMBAI’
REPL

79. DL/I CALL EXERCISE Continued ...
9. GET THE FIRST OFFERING OCCURRENCE WHERE THE LOCATION IS “CHENNAI”, TOGETHER WITH ITS PARENT COURSE OCCURRENCE
10. INSERT A NEW COURSE “ABC” TOGETHER WITH AN OFFERING AT CHENNAI ON 26 March 2002, FOR WHICH TEACHER IS EMPLOYEE NUMBER 12345
11. GET THE TEACHER OF THE FIRST OFFERING ATTENDED BY STUDENT
9. GU COURSE*D
OFFERING (LOCATION=‘CHENNAI’)
10. Build segments in I/O area
ISRT COURSE*D
OFFERING
TEACHER
NOTE: *D IS REQUIRED ONLY FOR FIRST SEGMENT
11. GU STUDENT (EMP#=222222)
GN OFFERING*V
TEACHER*F

80. DATABASE ACCESS METHODS
SESSION 8
DATABASE ACCESS METHODS

81. IMS DATABASE ACCESS METHODS
DL/I PROVIDES TWO BASIC DATABASE ORGANIZATIONS
HIERARCHICAL SEQUENTIAL (HS)
HIERARCHICAL DIRECT (HD)
Database Organization
Access Methods HS
HSAM - Hierarchical Sequential Access Method
HISAM - Hierarchical Indexed Sequential Access Method
SHSAM - Simple HSAM
SHISAM - Simple HISAM HD
HDAM - Hierarchical Direct Access Method
HIDAM - Hierarchical Indexed Direct Access Method
DL/I PROVIDES GSAM(Generalized Sequential Access Method) TO ACCESS NORMAL SEQUENTIAL DATASETS

82. IMS DATABASE ACCESS METHODS
Continued ...
HSAM / SHSAM
SEGMENTS OF A DATABASE RECORD ARE STORED IN SEQUENTIAL ORDER
VERY EFFICIENT FOR SEQUENTIAL PROCESSING
NEW SEGMENTS CAN NOT BE INSERTED. DATABASE HAS TO BE UNLOADED AND LOADED AGAIN.
ONCE DATABASE IS LOADED ONLY GET OPERATIONS ARE VALID (GU, GN , GNP, NOT “GET HOLD”)
ISRT CALL IS VALID ONLY WHILE LOADING NEW DATABASE
REPL AND DLET ARE NOT ALLOWED
SHSAM IS A SUBSET OF HSAM AND CONTAINS ONLY ROOT SEGMENTS
ONLY HSAM/SHSAM DATABASES CAN BE STORED ON A TAPE
SEGMENTS CAN NOT SPAN OVER RECORDS

83. IMS DATABASE ACCESS METHODS
Continued ...
HSAM SEGMENT STORAGE IN DATABASE
Delete byte
‘00’ -’FF’
‘00’
SEGMENT DATA
Segment Identifier
HSAM DBDGEN
DBD NAME=EXHSAM,ACCESS=HSAM
DATASET DD1=EXHSAMI,DD2=EXHSAMO,DEVICE=3380,RECORD=(512,512)
SEGM FIELD=…………….

84. IMS DATABASE ACCESS METHODS
Continued ...
HISAM / SHISAM
SIMILAR TO HSAM AND IN ADDITION INDEX IS ADDED FOR DIRECT ACCESS TO ROOT SEGMENT
VERY EFFICIENT FOR SEQUENTIAL AND FAIRLY GOOD FOR RANDOM PROCESSING
HISAM DATABASE REQUIRES TWO SEPARATE DATASETS
PRIMARY DATASET
OVERFLOW DATASET
OVERFLOW DATASET IS NOT REQUIRED FOR SHISAM
SEGMENTS CAN BE DELETED
PREFERABLE IF DATABASE HAS ROOT SEGMENTS ONLY

85. IMS DATABASE ACCESS METHODS
Continued ...
HISAM SEGMENT STORAGE IN DATABASE
4 Byte RBA
Delete byte
RBA
‘00’ -’FF’
‘00’
SEGMENT DATA
Segment Identifier
HISAM DBDGEN
DBD NAME=EXHISAM,ACCESS=(HISAM,VSAM)
DATASET DD1=HISAMPR,OVFLW=HISAMOV,DEVICE=3380,RECORD=(512,512)
SEGM FIELD=…………….

86. IMS DATABASE ACCESS METHODS
Continued ...
HDAM
DIRECT ADDRESS POINTERS TO RELATED SEGMENTS ARE STORED ALONG WITH SEGMENTS
VERY EFFICIENT FOR RANDOM PROCESSING BUT NOT FOR SEQUENTIAL PROCESSING
ROOT SEGMENTS ARE STORED ACCORDING TO SOME RANDOMIZING SCHEME
HDAM SEGMENT STORAGE IN DATABASE
Delete byte
‘00’ -’FF’
‘00’
POINTERS
SEGMENT DATA
Segment Identifier

87. IMS DATABASE ACCESS METHODS
Continued ...
HDAM DBDGEN
DBD NAME=EXHDAM,ACCESS=(HDAM,VSAM),RMNAME=(DFSHDC10,,10)
DATASET DD1=EXHDAM,DEVICE=3380
SEGM NAME=SEG1,BYTES=48,POINTER=TWIN
FIELD …………….
SEGM NAME=SEG2,PARENT=((SEG1,SNGL)),BYTES=32,POINTER=TWIN
…….

88. IMS DATABASE ACCESS METHODS
Continued ...
HIDAM
SIMILAR TO HDAM AND IN ADDITION INDEX TO ROOT SEGMENTS WILL BE STORED
EFFICIENT FOR BOTH SEQUENTIAL AND RANDOM PROCESSING
MOST COMMON TYPE OF DATABASE ORGANIZATION
HIDAM DBDGEN
DBD NAME=EXHIDAM,ACCESS=(HIDAM,VSAM),RMNAME=(DFSHDC10,,10)
DATASET DD1=EXHIDAM,DEVICE=3380
SEGM NAME=SEG1,BYTES=48,POINTER=TWIN
FIELD …………….
SEGM NAME=SEG2,PARENT=((SEG1,SNGL)),BYTES=32,POINTER=TWIN
…….

89. IMS DATABASE ACCESS METHODS
Continued ...
GSAM
COMPATIBLE WITH MVS DATASETS
NO HIERARCHY
CAN HAVE FIXED OR VARIABLE LENGTH RECORDS
NO DELETE OR REPLACE
INSERT ONLY AT THE END OF DATASET
GETS RECORDS SEQUENTIALLY
USUALLY USED WHEN CHECK/POINT RESTART IS USED

90. SESSION 9
MULTIPLE PROCESSING

91. MULTIPLE PROCESSING
MULTIPLE PROCESSING MEANS A PROGRAM CAN HAVE MORE THAN ONE POSITION IN A SINGLE DATABASE AT THE SAME TIME
ESTABLISHED BY
MULTIPLE PCBS
MULTIPLE POSITIONING
MULTIPLE PCBS CAN BE DEFINED AND USED FOR A SINGLE DATABASE TO ESTABLISH MULTIPLE POSITIONING HAS THE DRAWBACK OF IMPOSING OVERHEAD DUE TO THE EXTRA PCBS THUS CAUSING INEFFICIENCY

92. MULTIPLE PROCESSING Continued ...
MULTIPLE POSITIONING LETS A PROGRAM MAINTAIN MORE THAN ONE POSITION WITHIN A DATABASE USING A SINGLE PCB. THE PCB HAS TO BE CODED SUITABLY IN ORDER TO ACHIEVE THIS (POS=M)
MULTIPLE POSITIONING IS MORE EFFICIENT THAN USING MULTIPLE PCBS WHEREAS MULTIPLE PCBS OFFER MORE FLEXIBILITY

93. MULTIPLE PROCESSING EXAMPLE Continued ...
CALLS GN SEGMENTB, GN SEGMENTC, GN SEGMENTB, GN SEGMENTC A1 A2
C13
B13
B12
C12
B11
C11
C22
B22
B21
C21

94. SESSION 10
SECONDARY INDEXING

95. SECONDARY INDEXING
ALLOWS YOU TO ACCESS DB IN A SEQUENCE OTHER THAN PRIMARY SEQUENCE
ALLOWS YOU TO ACCESS A SEGMENT WITHOUT SUPPLYING ITS CONCATENATED KEY
THE SECONDARY INDEX ITSELF IS A DATABASE WITH ITS OWN DBD DEFINITION
SECONDARY INDEX DATABASE CONTAINS POINTER TO TARGET SEGMENT AND KEY VALUE OF SOURCE SEGMENT

96. SECONDARY INDEXING
SECONDARY INDEX DATABASE IS MAINTAINED AUTOMATICALLY BY DL/I SECONDARY DATA STRUCTURES
NEED TO USE PROCSEQ OPTION IN PCB STATEMENT OF PSBGEN MACRO ELSE DATABASE IS ACCESSED AS PER NORMAL HIERARCHY
DATABASE TO BE INDEXED MUST BE IN HISAM, HDAM, OR HIDAM, NOT IN HSAM
LIMITATIONS: 32 SECONDARY INDICES ON ONE SEGMENT TYPE
1000 SECONDARY INDICES FOR A DATABASE

97. SECONDARY INDEXING Continued ... Indexed Database Secondary Index DB
Prefix | Data
Customer
Pointer
Invoice No
Index pointer segment
Index
Target Segment
Ship-to
Index
Source Segment
Buyer
Receivable
Payment
Adjustment
Line Item

98. SECONDARY DATA STRUCTURE
Continued ...
SECONDARY INDEXING
SECONDARY DATA STRUCTURE
Receivable
Ship-to
Payment
Adjustment
Line Item
Customer
Buyer

99. SECONDARY INDEXING Indexed Database Secondary Index DB Continued ...
Prefix | Data
Customer
Pointer
Invoice No
Index pointer segment
Index
Target Segment
Ship-to
Index
Source Segment
Buyer
Receivable
Payment
Adjustment
Line Item

100. SECONDARY INDEXING Continued ... COURSE COURSE# TITLE DESCRIPN PREREQ
OFFERING
COURSE#
TITLE
DATE
LOCATION
FORMAT
TEACHER
STUDENT
EMPNUM
NAME
EMPNUM
NAME
GRADE

101. SECONDARY INDEXING Continued ...
INDEXING THE ROOT ON A FIELD NOT THE SEQUENCE FIELD
MAINDBD MACRO
DBD NAME=EDUCPDBD
SEGM NAME=COURSE,BYTES=256
FIELD NAME=(COURSE#,SEQ),BYTE3,START=1
FIELD NAME=TITLE,BYTES=33,START=4
LCHILD NAME=(TPTR,TXDBD),POINTER=INDX
XDFLD NAME=XTITLE,SRCH=TITLE
INDEX DBD MACRO
DBD NAME=TXDBD,ACCESS=INDEX
SEGM NAME=TPTR,BYTES=33
FIELD NAME=(TITLE,SEQ),BYTES=33,START=1
LCHILD NAME=(COURSE,EDUCPDBD),INDEX=XTITLE
PSB MACRO
PCB TYPE=DB,DBDNAME=EDUCPDBD,KEYLEN=15
PROCOPT=G,PROCSEQ=TXDBD
SENSEG NAME=COURSE
SENSEG NAME=OFFERING,PARENT=COURSE
SENSEG NAME=STUDENT,PARENT=OFFERING
SYNTAX: GU COURSE (XTITLE=‘DYNAMICS’)

102. SECONDARY INDEXING Continued ...
WHAT HAPPENS IF “PROCSEQ=TXDBD” IS NOT USED?
DL/I BY DEFAULT USES PRIMARY PROCESSING SEQUENCE

103. SECONDARY INDEXING Continued ...
INDEXING THE ROOT ON A FIELD IN THE DEPENDENT
MAINDBD MACRO
DBD NAME=EDUCPDBD
SEGM NAME=COURSE,BYTES=256
FIELD NAME=(COURSE#,SEQ),BYTE3,START=1
FIELD NAME=TITLE,BYTES=33,START=4
LCHILD NAME=(LPTR,LXDBD),POINTER=INDX
XDFLD NAME=XLOC,SRCH=LOCATION,SEGMENT=OFFERING
INDEX DBD MACRO
DBD NAME=LXDBD,ACCESS=INDEX
SEGM NAME=LPTR,BYTES=..
FIELD NAME=(LOCATION,SEQ),BYTES=….
LCHILD NAME=(COURSE,EDUCPDBD),INDEX=XLOC
SYNTAX: GU COURSE (XLOC=‘CHENNAI’)

104. LOGICAL RELATIONSHIPS
SESSION 11
LOGICAL RELATIONSHIPS

105. LOGICAL RELATIONSHIPS
RELATIONSHIP BETWEEN TWO SEGMENTS IN TWO PHYSICALLY SEPARATE DATABASES
CAN ALSO CONNECT TWO SEGMENTS WITHIN THE SAME DATABASE
ALLOWS APPLICATION TO HAVE DIRECT ACCESS FROM A SEGMENT IN ONE PHYSICAL DATABASE TO A LOWER LEVEL SEGMENT IN ANOTHER PHYSICAL DATABASE
RESULTS IN A NEW HIERARCHY- ONE THAT DOES NOT EXIST IN PHYSICAL STORAGE BUT CAN BE PROCESSED BY APPLICATION PROGRAMS AS THOUGH IT EXISTS
THREE TYPES OF LOGICAL RELATIONSHIPS
UNIDIRECTIONAL LOGICAL RELATIONSHIP
BIDIRECTIONAL PHYSICALLY PAIRED LOGICAL RELATIONSHIP
BIDIRECTIONAL VIRTUALLY PAIRED LOGICAL RELATIONSHIP

106. LOGICAL RELATIONSHIPS
Continued ...
LOGICAL RELATIONSHIPS
ORDER Database
Logical Parent
of DETAIL
PART Database
Physical Parent
of DETAIL
PART
ORDER
Logical Relationship
STOCK
DETAIL
SHIPMENT
Logical Children
of PART
Physical Children
of ORDER

107. LOGICAL RELATIONSHIPS
Continued ...
LOGICAL RELATIONSHIPS
PART /ORDER
Logical Database
ORDER/PART
Logical Database
PART
ORDER
STOCK
DETAIL
ORDER
DETAIL
PART
SHIPMENT
SHIPMENT
STOCK

108. SESSION 12
DB RECOVERY / RESTART

109. DATABASE RECOVERY
WHY?
TO RESTORE A DATABASE AFTER ITS PARTIAL DESTRUCTION
WHEN?
A DLI BATCH UPDATE JOB FAILS AFTER MAKING AT LEAST ONE DATABASE UPDATE
A FAILURE HAS OCCURRED ON A PHYSICAL DASD DEVICE
A FAILURE HAS OCCURRED IN A DATABASE RECOVERY UTILITY
A FAILURE OF DYNAMIC BACKOUT OR BATCH BACKOUT UTILITY HAS OCCURRED
AN IMS ONLINE SYSTEM FAILURE AND EMERGENCY RESTART HAS NOT BEEN COMPLETED

110. DATABASE RECOVERY Continued ... HOW? ONLINE RECOVERY PROCESS
IMS DOES DYNAMIC BACKOUT USING THE LOG INFORMATION FOR DL/I PROGRAMS
FOR BMP PROGRAMS UPDATES ARE AUTOMATICALLY BACKED OUT TO THE LAST CHECKPOINT
BATCH RECOVERY PROCESS
FORWARD RECOVERY
BACKWARD RECOVERY / BATCH BACK OUT

111. DATABASE RECOVERY UTILITIES FOR RECOVERY Continued ... DFSUDMP0:
DATABASE IMAGE COPY UTILITY FOR CREATION OF IMAGE COPIES OF DATABASES
DFSUCUM0:
DATABASE CHANGE ACCUMULATION UTILITY FOR ACCUMULATION OF DATABASE CHANGES FROM DL/I LOG TAPES SINCE THE LAST COMPLETE IMAGE COPY
DFSURDB0:
DATABASE RECOVERY UTILITY FOR RESTORATION OF THE DATABASE, USING A PRIOR DATABASE IMAGE COPY AND THE ACCUMULATED CHANGES FROM DL/I LOG TAPES
DFSBBO00:
DATABASE BACK OUT UTILITY FOR REMOVAL OF CHANGES MADE TO DATABASES BY A SPECIFIC APPLICATION PROGRAM

112. DATABASE RECOVERY DATABASE RECOVERY CONTROL (DBRC) Continued ...
DBRC INCLUDES THE IMS FUNCTIONS WHICH PROVIDE IMS SYSTEM AND DATABASE INTEGRITY AND RESTART CAPABILITY.
DBRC RECORDS INFO IN 3 RECON VSAM DATASETS
RECON CONTAINS FOLLOWING INFORMATION
LOG DATA SET INFORMATION
DATABASE DATA SET INFORMATION
ALLOCATION OF A DATABASE
UPDATE OF A DATABASE
IMAGE COPY OF A DATABASE
ABEND OF A SUBSYSTEM
RECOVERY OF A DATABASE
REORGANIZATION OF A DATABASE
DBRC AUTHORIZES OR REFUSES TO AUTHORIZE THE DATABASES DEPENDING ON THE CURRENT AUTHORIZATIONS AND THE ACCESS INTENT OF THE SUBSYSTEM.

113. DATABASE RECOVERY FORWARD RECOVERY Continued ...
RESTORE MOST RECENT IMAGE COPY DATASET
CHANGES MADE TO DATABASE SINCE THE LAST IMAGE COPY ARE APPLIED ON THE RESTORED DATABASE BY USING
CHANGE ACCUMULATION DATASETS
LOG DATASETS

114. DATABASE RECOVERY BACKWARD RECOVERY Continued ...
USES BATCH BACKOUT UTILITY TO DO A FULL BACKOUT OR BACKOUT TO ANY PRIOR CHECKPOINT
PSB USED IS SAME AS PSB OF THE PROGRAM WHOSE EFFECTS HAVE TO BE BACKED OUT
INPUTS
LOG DATASETS
DATABASES WHOSE UPDATES ARE TO BACKED OUT
CHECKPOINT ID
WARNING: DO NOT USE CHECKPOINT ID WHILE BACKING OUT BMP. IT TAKES BY DEFAULT THE LAST CHECKPOINT ISSUED.
OUTPUTS
BACKED OUT DATABASES

115. DATABASE RECOVERY Continued ...
HOW DO YOU BACK OUT A NORMALLY TERMINATED PROGRAM?
BY GIVING DBRC=C IN THE JCL SHOWN BELOW
//STEP1 EXEC PGM=DFSRRC00,
// REGION=5632K,
// PARM=(DLI,&MBR,&PSB,,
// &SPIE&TEST&EXCPVR&RST,&PRLD,
// &SRCH,&CKPTID,&MON,,&FMTO,,&SWAP,
// &DBRC,&IRLM,&IRLMNM,&BKO)
//*

116. DATABASE RECOVERY CHECKPOINT CALL (CHKP) Continued ...
CHECKPOINT RESTART IS USED DURING BACKWARD RECOVERY
CHECKPOINT COMMITS PROGRAMS UPDATES TO THE DATABASE AND LOGS THE UPDATES
TWO TYPES OF CHECKPOINTS
BASIC CHECKPOINT
STORES JUST CHECKPINT ID ( 8 BYTES STORED IN IO-AREA)
SYNTAX: CALL ‘CBLTDLI’ USING WS-CHKP, IO-PCB, IO-AREA
SYMBOLIC CHECKPOINT
STORES CRITICAL DATA APART FROM CHECKPOINT ID
MUST USE XRST FOR RESTARTING
SYNTAX: CALL ‘CBLTDLI’ USING WS-CHKP,
IO-PCB, IO-AREA-LEN, IO-AREA,
IO-AREA-LEN1, IO-AREA1…

117. IO-PCB, IO-AREA-LEN, IO-AREA,
DATABASE RECOVERY
Continued ...
RESTART CALL(XRST)
USED TO RESTART A PROGRAM AFTER ABNORMAL TERMINATION
RESTART FROM
SPECIFIC CHECKPOINT ID
TIME/DATESTAMP
LAST CHECKPOINT (‘LAST’) - BMPs ONLY
MUST BE THE FIRST CALL IN THE PROGRAM
SYNTAX: CALL ‘CBLTDLI’ USING WS-XRST,
IO-PCB, IO-AREA-LEN, IO-AREA,
IO-AREA-LEN1, IO-AREA1…

118. DATABASE RECOVERY FACTORS TO BE CONSIDERED FOR CHKP & XRST CALLS
Continued ...
FACTORS TO BE CONSIDERED FOR CHKP & XRST CALLS
ALL FILES (INCLUDING SYSIN, SYSOUT) USED BY PROGRAM SHOULD BE DL/I (GSAM) DATABASES OTHERWISE THERE WILL BE DUPLICATE DATA OR LOSS OF DATA
GSAM OUTPUT FILES SHOULD USE DISP=(NEW,KEEP,KEEP) FOR INITIAL RUN AND DISP=(OLD,KEEP,KEEP) FOR RESTARTS

119. EFFICIENT PROGRAMMING TIPS
SESSION 13
EFFICIENT PROGRAMMING TIPS

120. PROGRAMMING TIPS
INSTEAD OF USING GET CALL PRECEDING A ISRT CALL USE ISRT WITH APPROPRIATE SSA
USE QUALIFIED SSAS WHEREVER POSSIBLE
IMPLIED SSAS SHOULD BE AVOIDED EVENTHOUGH DL/I CONSTRUCTS MISSING SSAS
MINIMIZE THE NUMBER OF DL/I CALLS BY USING COMMAND CODES
USE SEARCH FIELDS IN DL/I CALLS INSTEAD OF USING IF STATEMENTS IN COBOL PROGRAM

121. PROGRAMMING TIPS Continued ... TRY USING SECONDARY INDICES
DESIGN YOUR PROGRAM TO RUN IN BOTH BMP AND BATCH MODE
USE CHECKPOINT/RESTART
THERE IS ONLY A SMALL PERFORMANCE DIFFERENCE BETWEEN THE GET AND GET HOLD CALLS. SO USE GET HOLD CALLS WHENEVER THERE IS A CHANCE ( > 5%) OF SEGMENT UPDATE/DELETE
IT IS GOOD PRACTICE TO PROGRAM FOR EASY ADJUSTMENT OF CHECKPOINT FREQUENCY

122. SESSION 14
COMMON IMS ABENDS

123. COMMON IMS ABENDS U0047 DESCRIPTION
ONE OF THE DBPCBS IN THE PSB FAILED TO OBTAIN THE DATABASE AUTHORIZATION THROUGH DBRC. USUALLY OCCURS WHEN DATABASE IS UP IN ONLINE OR DATABASE IS USED IN UPDATE MODE BY ANOTHER PROGRAM.
SOLUTION
BRING DOWN THE DATABASE USING /DBR DB DATABASE NAME
WAIT TILL CONTENDING JOB COMPLETES AND RESTART THE JOB

124. COMMON IMS ABENDS U0456 DESCRIPTION
A DL/I BATCH REGION, BMP PROGRAM COULD NOT BE INITIATED BECAUSE THE PSB HAS BEEN STOPPED OR LOCKED BY A COMMAND OR A PRIOR PROGRAM FAILURE
SOLUTION
ANALYZE WHY THE PSB IS LOCKED OR STOPPED. RESTART THE JOB AFTER THE PSB HAS BEEN UNLOCKED
TO UNLOCK PSB FOR A BMP PROGRAM USE /START PROGRAM psbname COMMAND

125. COMMON IMS ABENDS U0476 DESCRIPTION
A DL/I CALL DOES NOT INCLUDE A VALID PCB ADDRESS
PROBABLE CAUSES
PSB LANGUAGE TYPE SPECIFIED IS NOT SAME AS THAT OF APPLICATION PROGRAM
COBOL MAIN PROGRAM ENTERED AT PROCEDURE DIVISION INSTEAD OF DLITCBL BECAUSE ENTRY DLITCBL NOT INCLUDED IN LKED
WRONG PCB WITH FEWER PCBS THAN EXPECTED IS USED

126. COMMON IMS ABENDS U0852 DESCRIPTION
THE SEGMENT CODE RETURNED IS NOT VALID FOR THE DATABASE
SOLUTION
ANALYZE THE DATABASE. IF THERE IS AN INVALID POINTER, RECOVER THE DATABASE.

127. COMMON IMS ABENDS U3303 DESCRIPTION
APPLICATION PROGRAM TRIED TO USE A DATABASE THAT WAS NOT AVAILABLE FOR ACCESS AND/OR UPDATE. DFS3303I MESSAGE ACCOMPANIES THIS ABEND
SOLUTION
CHECK THE STATUS OF DATABASE GIVEN IN DFS3303I MESSAGE USING
/DISPLAY DB database name
IF DATABASE IS DOWN START THE DATABASE USING THE COMMAND
/START DB database name