IMS - DB
1
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
2
SESSION 1
IMS GENERAL CONCEPTS
3
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
4
Continued ...
HIERARCHICAL STRUCTURE
ROOT SEGMENT (PARENT)
FOLLOWS INVERTED TREE STRUCTURE
A2
-- Level 1
A1
EACH BOX IN THE HIERARCHY REPRESENTS
A SEGMENT
SEGMENT OCCURRNCES
ROOT SEGMENT WILL BE ON TOP
EACH SEGMENT (EXCEPT ROOT SEGMENT)
B3
B1
B2
TWIN SEGMENTS
IS DIRECTLY DEPENDENT ON ONLY ONE
C1
D1
-- Level 2
SEGMENT
DEPENDENT SEGMENTS
5
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
6
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
7
IMS GENERAL
CONCEPTS
Continued
...
TYPES OF SEGMENTS
ROOT
A SEGMENT WITHOUT PARENT
A SEGMENT WITH ONE OR MORE DEPENDENT SEGMENTS
PARENT
DIRECTLY UNDER IT
A SEGMENT WHICH IS DIRECTLY DEPENDENT ON ANOTHER
CHILD
DEPENDENT
TWIN
SIBLINGS
SEGMENT
ALL SEGMENTS UNDER A PARTICULAR SEGMENT OF THE
DATABASE
ALL OCCURRENCES (2 OR MORE) OF A SEGMENT TYPE
UNDER A PARENT
OCCURRENCES OF DIFFERENT SEGMENT TYPES UNDER
A PARENT
8
Continued ...
EXERCISE - 1
1
2
5
6
3
7
4
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?
9
Continued ...
DATABASE RECORD
ONE OCCURRENCE OF A ROOT SEGMENT ALONG WITH ALL ITS DEPENDENT
SEGMENTS
10
Continued ...
EXERCISE-2
HOW MANY DATABASE RECORDS?
11
IMS GENERAL
CONCEPTS
Continued
...
IMS DATABASE LIMITATIONS
IMS SUPPORTS
15 LEVELS
255 SEGMENTS
1000 FIELDS
NO LIMITATION ON NUMBER OF SEGMENT OCCURRENCES.
12
IMS GENERAL
CONCEPTS
Continued
...
IMS ENVIRONMENT
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
App Prog
DB PCB
interface
I/O PCB
interface
DL/I
DC
Database
Terminal
DL/I ALLOWS SEQUENTIAL OR
RANDOM PROCESSING OF DATABASE
13
IMS GENERAL
CONCEPTS
Continued
...
IMS ENVIRONMENT
MODES OF PROCESSING
BATCH DL/I MODE
MPP MODE
BMP MODE
ONLINE
MPP
BATCH
BMP
DL/I
14
IMS GENERAL
CONCEPTS
Continued
...
IMS ENVIRONMENT
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
15
IMS GENERAL
CONCEPTS
Continued
...
IMS ENVIRONMENT
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
16
SESSION 2
DL/I CONTROL BLOCKS
17
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
18
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
SPECIFIES FIELD NAME, LENGTH, STARTING POSITION
IDENTIFIES A FIELD AS KEY OR SEARCH FIELD
FIELD
19
DL/I CONTROL
BLOCKS
Continued
...
SAMPLE DBDGEN
PRINT
DBD
DATASET
SEGM
FIELD
SEGM
FIELD
SEGM
FIELD
FIELD
DBDGEN
FINISH
END
NOGEN
NAME=VENDOR,ACCESS=HDAM
DD1=VEND,DEVICE=3380
NAME=VENSEG,PARENT=0,BYTES=10
NAME=(VENCODE,SEQ,U),BYTES=10,START=1,TYPE=C
NAME=ITEMSEG,PARENT=VENSEG,BYTES=5
NAME=(ITEMCODE,SEQ,U),BYTES=5,START=1,TYPE=C
NAME=LOCNSEG,PARENT=ITEMSEG,BYTES=9
NAME=(LOCNCODE,SEQ),BYTES=3,START=1,TYPE=C
NAME=ORDDATE,BYTES=6,START=4,TYPE=C
20
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
21
DL/I CONTROL
BLOCKS
Continued
...
CAN WE DEFINE OVERLAPPING FIELDS?
22
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
23
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
B
A
C
D
C
E
E
24
DL/I CONTROL
BLOCKS
Continued
...
SAMPLE PSBGEN
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
25
DL/I CONTROL
BLOCKS
Continued
...
PROCOPTS IN PSB DEFINES SECURITY LEVEL FOR THE PROGRAM
DESCRIPTION
PROCOPT
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
26
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
DBD1
PCB4
DBD2
DBD3
27
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. 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
28
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=_____________________
SENSEG NAME=_________________,PARENT=_____________________
SENSEG NAME=_________________,PARENT=_____________________
SENSEG NAME=_________________,PARENT=_____________________
PSBGEN LANG=COBOL,PSBNAME=EMPPSBY
END
29
SESSION 3
SEGMENT SEARCH ARGUMENT
30
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
31
ContinuedARGUMENT
...
SEGMENT SEARCH
WHAT IS THE SIGNIFICANCE OF MAX 15 SSA?
32
ContinuedARGUMENT
...
SEGMENT SEARCH
TYPES OF SSAS
UNQUALIFIED
SEARCHES FOR A SPECIFIC SEGMENT TYPE
QUALIFIED
SEARCHES FOR A SPECIFIC SEGMENT OCCURRENCE
MORE EFFICIENT THAN UNQUALIFIED SSA
33
ContinuedARGUMENT
...
SEGMENT SEARCH
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
*
-
34
ContinuedARGUMENT
...
SEGMENT SEARCH
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 ‘123456789000’ TO KEY-VALUE.
CALL ‘CBLTDLI’ USING FUNC-CODE, PCB-MASK-1, IO-AREA, SSA-EMPLOYEE.
35
ContinuedARGUMENT
...
SEGMENT SEARCH
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’, ‘>=‘, ‘=>’
36
ContinuedARGUMENT
...
SEGMENT SEARCH
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”
37
SESSION 4
COBOL BASICS FOR IMS
38
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
FUNCTION CODES
ENVIRONMENT DIVISION
I/O AREA
DATA DIVISION
FILE SECTION
WORKING STORAGE SECTION
LINKAGE SECTION
SEGMENT SEARCH ARGUMENTS
PCB MASKS
PROCEDURE DIVISION
39
COBOL BASICS
IMS
ContinuedFOR
...
FUNCTION CODES
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
40
COBOL BASICS
IMS
ContinuedFOR
...
INPUT/OUTPUT AREA
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
41
COBOL BASICS
IMS
ContinuedFOR
...
THE PCB MASK
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
42
COBOL BASICS
IMS
ContinuedFOR
...
THE PCB MASK
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
43
COBOL BASICS
IMS
ContinuedFOR
...
PROCEDURE DIVISION
PROCEDURE DIVISION.
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.
44
COBOL BASICS
IMS
ContinuedFOR
...
RUN JCL EXECUTES THE BATCH PROCESSOR
DFSRRC00 AND PASSES THE APPLICATION
PROGRAM NAME AND PSBNAME AS
PARAMETERS
RUN JCL
ENTRY DLITCBL PASSES THE PCB ADDRESS TO
THE PROGRAM
PROGRAM NAME
PSB NAME
IMS
DATABASE
CBLTDLI
GOBACK
DLITCBL
DL/I
APPLICATION
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
45
SESSION 5
DL/I CALLS
46
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
47
DL/I
CALLS
Continued
...
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
11
7
BKEY
2
EKEY
8
6
4
10
3
5
CKEY
9
DKEY
FKEY
EXERCISE: WRITE A GU TO RETRIEVE FKEY=10
48
DL/I
CALLS
Continued
...
WHAT WILL BE THE OUTPUT OF A GU CALL WITH NO SSA?
49
DL/I
CALLS
Continued
...
GET NEXT
RETREIVAL SEQUENCE
TOP TO BOTTOM
FRONT TO BACK
AKEY
1
LEFT TO RIGHT
EKEY
11
7
BKEY
2
8
GA
6
4
10
3
5
9
GK
CKEY
DKEY
FKEY
50
DL/I
CALLS
Continued
...
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
AKEY
1
7
EKEY
11
2
BKEY
8
6
4
3
10
5
CKEY
9
DKEY
FKEY
EXERCISE: WHAT WILL BE THE RESULTS OF FOUR CONSEQUETIVE GNs AFTER EKEY=8 IS RETRIEVED
51
DL/I
CALLS
Continued
...
GET NEXT WITHIN PARENT
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
2
BKEY
EKEY
8
6
4
3
10
5
CKEY
9
DKEY
FKEY
52
DL/I
CALLS
Continued
...
WHAT WILL BE THE OUTPUT IF GNP IS DONE 4 MORE TIMES IN
PREVIOUS EXAMPLE?
53
DL/I
CALLS
Continued
...
PATH CALLS EXERCISE
‘CBLTDLI’ USING ‘GN ‘, LS-PCB-MASK, WS-SEG-IO-AREA,
CALL
SEGMENTA*D(AKEY=1)
SEGMENTF*-(FKEY=10)
WHAT WILL BE THE RESULT AFTER SUCCESSFUL COMPLETION OF THE ABOVE
CALL?
1
11
7
2
BKEY
EKEY
8
6
4
3
10
5
CKEY
9
DKEY
FKEY
54
DL/I
CALLS
Continued
...
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
55
DL/I
CALLS
Continued
...
DELETE/REPLACE CALLS
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
56
DL/I
CALLS
Continued
...
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
2
BKEY
EKEY
8
6
4
3
10
5
CKEY
9
DKEY
WHAT WILL BE THE RESULT IF THE FIRST GHU CALL IS SEGMENTA*D(AKEY=1)?
57
DL/I
CALLS
Continued
...
REPLACE (REPL)
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
58
DL/I
CALLS
Continued
...
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
2
BKEY
EKEY
8
6
4
3
10
5
CKEY
9
DKEY
FKEY
59
DL/I
CALLS
Continued
...
INSERT (ISRT)
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
60
DL/I
CALLS
Continued
...
INSERT (ISRT)
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
61
DL/I
CALLS
Continued
...
MOVE DATA FOR SEGMENTE INTO WS-SEGMENT-IO-AREA WITH EKEY=99
‘CBLTDLI’ USING ‘ISRT’, LS-PCB-MASK, WS-SEGMENT-IO-AREA,
CALL
SEGMENTA*-(AKEY=1)
SEGMENTE
AFTER THE CALL SEGMENTE WITH EKEY=99 IS INSERTED
1
99
11
7
2
BKEY
EKEY
8
6
4
3
10
5
CKEY
9
DKEY
FKEY
62
DL/I
CALLS
Continued
...
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
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
63
DL/I
CALLS
Continued
...
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
64
SESSION 6
COMMAND CODES
65
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
66
COMMAND
CODES
Continued
...
SOME COMMAND CODES
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
67
COMMAND
CODES
Continued
...
COMMAND CODE “D”
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”
68
COMMAND
CODES
Continued
...
COMMAND CODE “D”
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
69
COMMAND
CODES
Continued
...
PATH CALLS EXAMPLE
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
2
BKEY
EKEY
8
6
4
3
10
5
CKEY
9
DKEY
FKEY
70
COMMAND
CODES
Continued
...
COMMAND CODE “F”
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
SEGMENTB
3
SEGMENTC
71
COMMAND
CODES
Continued
...
COMMAND CODE “L”
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
SEGMENTB
SEGMENTC
72
COMMAND
CODES
Continued
...
COMMAND CODE “N”
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
73
COMMAND
CODES
Continued
...
COMMAND CODE “P”
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
2
SEGMENTA
3
SEGMENTB
SEGMENTC
74
SESSION 7
DL/I CALL EXERCISE
75
DL/I CALL
EXERCISE
Continued
...
COURSE
COURSE#
TITLE
PREREQ
COURSE#
DESCRIPN
OFFERING
TITLE
DATE
TEACHER
EMPNUM
LOCATION
FORMAT
STUDENT
NAME
EMPNUM
NAME
GRADE
76
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
77
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”
78
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 222222
79
SESSION 8
DATABASE ACCESS METHODS
80
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
81
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
82
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=…………….
83
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
84
IMS DATABASE ACCESS
METHODS
Continued ...
HISAM SEGMENT STORAGE IN DATABASE
4 Byte RBA
RBA
‘00’ -’FF’
Delete byte
‘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=…………….
85
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
86
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
…….
87
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
…….
88
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
89
SESSION 9
MULTIPLE PROCESSING
90
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
91
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
92
MULTIPLE
PROCESSING
Continued
...
EXAMPLE
CALLS
GN SEGMENTB, GN SEGMENTC, GN SEGMENTB, GN SEGMENTC
A1
A2
C13
B13
B12
B11
C12
C11
C22
B22
B21
C21
93
SESSION 10
SECONDARY INDEXING
94
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
95
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
96
Continued
...
SECONDARY
INDEXING
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
97
Continued
...
SECONDARY
INDEXING
SECONDARY DATA STRUCTURE
Receivable
Ship-to
Customer
Payment
Adjustment
Line Item
Buyer
98
Continued
...
SECONDARY
INDEXING
Indexed Database
Secondary Index DB
Prefix | Data
Customer
Pointer Invoice No
Index
Index pointer
segment
Target Segment
Ship-to
Index
Source Segment
Buyer
Receivable
Payment
Adjustment
Line Item
99
Continued
...
SECONDARY
INDEXING
COURSE
COURSE#
TITLE
PREREQ
COURSE#
DESCRIPN
OFFERING
TITLE
DATE
TEACHER
EMPNUM
LOCATION
FORMAT
STUDENT
NAME
EMPNUM
NAME
GRADE
10
0
Continued
...
SECONDARY
INDEXING
INDEXING THE ROOT ON A FIELD NOT THE SEQUENCE FIELD
MAINDBD MACRO
INDEX DBD MACRO
DBD
SEGM
FIELD
FIELD
LCHILD
XDFLD
DBD
SEGM
FIELD
LCHILD
NAME=EDUCPDBD
NAME=COURSE,BYTES=256
NAME=(COURSE#,SEQ),BYTE3,START=1
NAME=TITLE,BYTES=33,START=4
NAME=(TPTR,TXDBD),POINTER=INDX
NAME=XTITLE,SRCH=TITLE
NAME=TXDBD,ACCESS=INDEX
NAME=TPTR,BYTES=33
NAME=(TITLE,SEQ),BYTES=33,START=1
NAME=(COURSE,EDUCPDBD),INDEX=XTITLE
PSB MACRO
PCB
SYNTAX:
SENSEG
SENSEG
SENSEG
TYPE=DB,DBDNAME=EDUCPDBD,KEYLEN=15
PROCOPT=G,PROCSEQ=TXDBD
NAME=COURSE
NAME=OFFERING,PARENT=COURSE
NAME=STUDENT,PARENT=OFFERING
GU
COURSE (XTITLE=‘DYNAMICS’)
10
1
Continued
...
SECONDARY
INDEXING
WHAT HAPPENS IF “PROCSEQ=TXDBD” IS NOT USED?
DL/I BY DEFAULT USES PRIMARY PROCESSING
SEQUENCE
10
2
Continued
...
SECONDARY
INDEXING
INDEXING THE ROOT ON A FIELD IN THE DEPENDENT
MAINDBD MACRO
INDEX DBD MACRO
DBD
SEGM
FIELD
FIELD
LCHILD
XDFLD
DBD
SEGM
FIELD
LCHILD
NAME=EDUCPDBD
NAME=COURSE,BYTES=256
NAME=(COURSE#,SEQ),BYTE3,START=1
NAME=TITLE,BYTES=33,START=4
NAME=(LPTR,LXDBD),POINTER=INDX
NAME=XLOC,SRCH=LOCATION,SEGMENT=OFFERING
SYNTAX:
GU
NAME=LXDBD,ACCESS=INDEX
NAME=LPTR,BYTES=..
NAME=(LOCATION,SEQ),BYTES=….
NAME=(COURSE,EDUCPDBD),INDEX=XLOC
COURSE (XLOC=‘CHENNAI’)
10
3
SESSION 11
LOGICAL RELATIONSHIPS
10
4
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
10
5
...
LOGICAL Continued
RELATIONSHIPS
Logical Parent
PART Database
ORDER Database
of DETAIL
Physical Parent
PART
ORDER
of DETAIL
Logical Relationship
STOCK
DETAIL
SHIPMENT
Logical Children
Physical Children
of PART
of ORDER
10
6
...
LOGICAL Continued
RELATIONSHIPS
PART /ORDER
ORDER/PART
Logical Database
Logical Database
PART
STOCK
DETAIL
SHIPMENT
ORDER
ORDER
DETAIL
PART
SHIPMENT
STOCK
10
7
SESSION 12
DB RECOVERY / RESTART
10
8
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
10
9
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
11
0
DATABASE
RECOVERY
Continued
...
UTILITIES FOR RECOVERY
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
111
DATABASE
RECOVERY
Continued
...
DATABASE RECOVERY CONTROL (DBRC)
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.
11
2
DATABASE
RECOVERY
Continued
...
FORWARD RECOVERY
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
11
3
DATABASE
RECOVERY
Continued
...
BACKWARD RECOVERY
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
LOG DATASETS
11
4
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)
11
5
DATABASE
RECOVERY
Continued
...
CHECKPOINT CALL (CHKP)
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…
11
6
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…
11
7
DATABASE
RECOVERY
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
11
8
SESSION 13
EFFICIENT PROGRAMMING TIPS
11
9
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
12
0
Continued ... TIPS
PROGRAMMING
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
12
1
SESSION 14
COMMON IMS ABENDS
12
2
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
12
3
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
12
4
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
12
5
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.
12
6
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
12
7