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COBOL Considerations

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COMMUNICATION-AREA (Your copy!) RESPONSE-CODE PIC S9(08) COMP. RECORD Descriptions ... If you don't code it, CICS Will! The commarea (if any) placed here! ... – PowerPoint PPT presentation

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Title: COBOL Considerations


1
COBOL Considerations
  • Identification Division.
  • No differences
  • Environment Division
  • MUST be EMPTY in CICS Program!
  • No SELECT statements allowed!
  • Data Division
  • No FILE SECTION (No SELECTS)

2
COBOL Considerations (More)
  • Data Division
  • WORKING-STORAGE SECTION.
  • Switches, Flags, Variables, Records, etc.
  • You get fresh copy each time program loaded!
  • LINKAGE SECTION (New Item!!)
  • DFHCOMMAREA defined or CICS will!
  • Used to receive data from CICS.
  • CICS also inserts EIB Block definition

3
COBOL Considerations (More)
  • Procedure Division
  • Uses most COBOL statements
  • Also uses CICS Commands like
  • RETURN
  • XCTL
  • SEND MAP
  • RECEIVE MAP
  • READ DATASET

4
Where are WE?
  • Program must be able to determine!
  • Always starts at beginning of Program
  • Starts with initialized Working-Storage
  • Can use several methods
  • EIBCALEN (First time program loaded)
  • COMMAREA (Tran-ID, EIBAID)
  • Hidden Data on Screen

5
Where are We? (More)
  • Beginning of Program must determine!
  • Can use series of IF statements
  • Can be nested (or not if careful!)
  • Usually each path ends with RETURN
  • Can use EVALUATE statement
  • EVALUATE TRUE most common (New Dev)
  • General WHEN OTHER for errors

6
Sample CICS COBOL Program
  • WORKING-STORAGE SECTION.
  • Switches, Flags, and Misc Variables
  • COMMUNICATION-AREA (Your copy!)
  • RESPONSE-CODE PIC S9(08) COMP.
  • RECORD Descriptions
  • COPY Library for MAP
  • Other COPY Members as needed

7
Sample CICS COBOL Program
  • LINKAGE SECTION.
  • DFHCOMMAREA PIC X(nnn).
  • If you dont code it, CICS Will!
  • The commarea (if any) placed here!
  • EIBCALEN gives length of commarea
  • 0 (ZERO) means there is NO commarea

8
Sample CICS COBOL Program
  • PROCEDURE DIVISION (Where are we?)
  • IF first-time
  • SEND Initial-Map
  • ELSE
  • IF
  • Process Screen
  • ELSE
  • Process Function-Key
  • END-IF
  • END-IF
  • SEND MAP

9
Sample CICS COBOL Program
  • PROCEDURE DIVISION
  • EVALUATE TRUE
  • WHEN EIBCALEN 0
  • First time in Program
  • WHEN EIBAID DFHENTER
  • Process Screen
  • WHEN EIBAID DFHPF3 or DFHPF12
  • Exit Program
  • WHEN OTHER
  • Invalid key
  • END-EVALUATE

10
Basic CICS Commands
  • General Structure
  • EXEC CICS
  • CICS COMMAND
  • OPTION(value)
  • (Parameters as needed)
  • END-EXEC

11
Basic CICS Commands
  • EXEC CICS
  • RETURN TRANSID(name)
  • COMMAREA(data-area)
  • LENGTH(data-value)
  • END-EXEC
  • Length PIC S9(4) COMP or Literal

12
Basic CICS Commands
  • EXEC CICS
  • XCTL PROGRAM(name)
  • COMMAREA(data-area)
    LENGTH(data-value)
  • END-EXEC

13
Basic CICS Commands
  • EXEC CICS
  • SEND MAP(name)
  • MAPSET(name)
  • FROM(data-area)
  • MAPONLY DATAONLY
  • ERASE ERASEUP
  • CURSOR (value)
  • END-EXEC

14
Basic CICS Commands
  • EXEC CICS
  • RECEIVE MAP(map-name)
  • MAPSET(mapset-name)
  • INTO(data-area)
  • END-EXEC

15
Basic CICS Commands
  • EXEC CICS
  • READ DATASET(filename)
  • INTO(data-area)
  • RIDFLD(data-area)
  • RRN RBA
  • UPDATE
  • END-EXEC

16
Basic CICS Commands
  • EXEC CICS
  • ABEND ABCODE(name)
  • END-EXEC
  • (ABCODE used to identify storage dump -
  • Usually omitted!)

17
CICS Program Design
  • Event-driven design
  • Structure Chart - Consider All Functions
  • Identify Events and Context
  • Any action that starts program
  • List All (Valid) Possible User Actions
  • Design Appropriate Response
  • Processing required for an event
  • Managing user interaction

18
CICS Program Design
  • COMMAREA usually stores context
  • Get Key
  • Add Customer
  • Change Customer
  • Delete Customer
  • Response to same key can be different depending
    on context (ENTER key)

19
CICS Program Design
  • Event/Response Chart
  • Helps with design or Program
  • Serves as Documentation of Program
  • Sometimes replaced with Structure Chart
  • Structure Chart Evolves into Design
  • Start with Major Functions
  • Add Detail as Needed
  • Assign Paragraph Numbering (If Used)

20
More CICS Commands
  • EXEC CICS
  • WRITE DATASET(filename)
  • FROM(data-area)
  • RIDFLD(data-area)
  • RRN RBA
  • END-EXEC

21
More CICS Commands
  • EXEC CICS
  • REWRITE DATASET(filename)
  • FROM(data-area)
  • END-EXEC
  • NOTES
  • Record MUST be READ with UPDATE!
  • data-area - NOT have to match Read

22
More CICS Commands
  • EXEC CICS
  • DELETE DATASET(filename)
  • RIDFLD(data-area)
  • RRN RBA
  • END-EXEC
  • NOTE If no RIDFLD last READ is Deleted

23
More CICS Commands
  • EXEC CICS
  • UNLOCK DATASET(filename)
  • END-EXEC
  • NOTE If READ/UPDATE command is used and you
    determine that record does not need to be
    updated. Usually not needed as record is unlocked
    when the task is terminated.

24
Exception Conditions
  • Most Common Exceptions
  • DISABLED Dataset disabled
  • DUPREC Record already exists
  • FILENOTFND Dataset not in FCT
  • INVREQ Invalid request
  • IOERR File I/O error
  • NOTAUTH User not authorized
  • NOTFND Record not in file

25
Checking for Exceptions
  • ALL CICS Commands allow RESP Parm
  • 01 RESP-CODE PIC S9(8) COMP.
  • IF RESP-CODE DFHRESP(NORMAL)
  • MOVE Y TO OK-COMMAND
  • ELSE
  • IF RESP-CODE DFHRESP(NOTFND)
  • MOVE N TO REC-NOT-FOUND
  • ELSE
  • PERFORM DISPLAY-MISC-ERROR
  • END-IF
  • END-IF

26
Preventing File Corruption
  • PREVENT
  • Add busy flag in record (Special Maint)
  • All programs MUST follow procedure
  • Extra I/O required (to Set/Reset flag)
  • DETECT
  • Save copy and compare before updating
  • OR Add Maint-Timestamp and check it
  • Notify User to get latest version of data

27
Avoiding Deadlock
  • Sometimes called Deadly Embrace
  • Happens when records from multiple files must be
    updated as a unit
  • Withdraw from Savings Deposit to Check
  • Crash after withdraw? Wheres money?
  • Must both be done or neither! (Atomic)

28
Program Control Commands
  • EXEC CICS
  • RETURN TRANSID(name)
  • COMMAREA(data-area)
  • LENGTH(data-value)
  • END-EXEC

29
Program Control Commands
  • EXEC CICS
  • LINK PROGRAM(name)
  • COMMAREA(data-area)
  • LENGTH(data-value)
  • END-EXEC
  • NOTE Program name must be in PPT.
  • Works like COBOL PERFORM statement.

30
Program Control Commands
  • EXEC CICS
  • XCTL PROGRAM(name)
  • COMMAREA(data-area)
  • LENGTH(data-value)
  • END-EXEC
  • NOTE Program name must be in PPT.

31
Terminal Handling
  • CURSOR Positioning (in SEND MAP)
  • IC option in DFHMDF Macro (ATTRB Parm)
  • If more than one LAST position is used.
  • DIRECT Cursor Positioning
  • CURSOR(nnn) where nnn is position on screen
  • Displacement from start of the screen
  • ( Row 1 ) 80 ( Column 1 )
  • 0 is Row 1, Column 1
  • 1919 is Row 24, Column 80 (24 by 80 Screen)
  • Changes in screen require changes to program
  • (Not used much - too complex!)

32
Terminal Handling (More)
  • CURSOR Positioning (in SEND MAP)
  • Symbolic Cursor Positioning (Preferred!)
  • CURSOR with no position parameter!
  • Specify the FIELD where the CURSOR goes
  • Place 1 in the LENGTH Attribute of the field
    where the cursor is to be placed
  • FIELD NAME with L appended is LENGTH
  • If more than one FIRST position is used.
  • BINARY HALFWORD - PIC S9(04) COMP.

33
Terminal Handling (More yet)
  • Determining the position of CURSOR when the user
    types an AID key.
  • EIBCPOSN in EIB Block (binary halfword)
  • READ only-Available before RECEIVE MAP
  • Can be used to determine user selection instead
    of requiring user to enter character

34
Attribute Modification
  • Symbolic Map includes Attribute byte
  • Field Name with A appended
  • Cryptic bit codes and names used
  • Copy library supplied by IBM (Horrible)
  • Most shops have their own copy book
  • We dont have extended attributes!

35
Editing Input Data
  • All data entered should be validated
  • Required data must be present
  • Numeric data needs to be normalized
  • Alpha data should not be spaces
  • Meaningful error messages displayed
  • Very tedious coding required!
  • Do checking from bottom to top!

36
Misc CICS Commands
  • EXEC CICS
  • SEND TEXT FROM(data-area)
  • LENGTH(data-value)
  • ERASE
  • FREEKB
  • END-EXEC
  • NOTE No FREEKB user must hit RESET!

37
Misc CICS Commands
  • EXEC CICS
  • HANDLE AID
  • option(procedure name)
  • END-EXEC

38
Misc CICS Commands
  • HANDLE AID Options
  • PA1-PA3 Program Attention Keys
  • PF1-PF24 Program Function Keys
  • ENTER The ENTER Key
  • CLEAR The CLEAR Key
  • ANYKEY Any key not Specified
  • (Except the ENTER key)

39
Handle AID Example (Old)
  • EXEC CICS
  • HANDLE AID PF3(900-MENU)
  • CLEAR(850-CLEAR)
  • ENTER(700-ENTER)
  • ANYKEY(750-ERROR)
  • END-EXEC
  • NOTE HANDLE AID sets up RECEIVE MAP!
  • Not executed when encountered! In OLD Progs.

40
Error Processing
  • There are over 70 CICS error Conditions
  • Mercifully only a few are handled
  • TWO Methods of handling exceptions
  • HANDLE CONDITION (Old Method)
  • Similar in function to HANDLE AID
  • RESPONSE Code checking
  • Allows cleaner program structure

41
Strange Exception - MAPFAIL
  • MAPFAIL Condition
  • Raised by RECEIVE MAP with no data
  • User entered no data but pressed AID key
  • User pressed CLEAR key or PA key
  • Simplest to PREVENT it from occurring
  • Check EIBAID to see what key was pressed
  • Dont issue RECEIVE MAP if PA or CLEAR hit
  • Include DUMMY field with MDT set ON

42
HANDLE CONDITION (Old!)
  • EXEC CICS
  • HANDLE CONDITION
  • condition(procedure-name)
  • condition(procedure-name)
  • up to 16 per statement
  • END-EXEC

43
HANDLE CONDITION
  • Common CONDITIONS
  • DUPREC Record already exists
  • MAPFAIL No data sent by user
  • NOSPACE No space left in file
  • NOTOPEN Data set not OPEN
  • NOTFND Record not in file
  • PGMIDERR Program not in PPT
  • ERROR ALL conditions not coded

44
HANDLE CONDITION Example
  • EXEC CICS
  • HANDLE CONDITION
  • MAPFAIL(500-NO-DATA)
  • DUPREC(600-DUPLICATE)
  • NOTOPEN
  • END-EXEC
  • NOTE Condition by itself will nullify it!

45
HANDLE CONDITION (Notes)
  • Not an executable command
  • Establishes paragraph to correct error
  • Can issue multiple times
  • Last one executed is in effect
  • Causes GO TO to paragraph named
  • Done BEFORE CICS Command executed
  • OLD method of coding AVOID!

46
RESPONSE CHECKING (NEW!)
  • ADD RESP option to CICS Command
  • Define binary fullword PIC S9(8) COMP
  • Name that field in each RESP option
  • COPY of EIBRESP from EIB
  • EIBRESP2 (RESP2) also available
  • Not many CICS Commands use it
  • Seldom needed as RESP is usually enough

47
USE General ERROR Handling
  • Most good shops have a standard error handling
    method
  • If not, use sample linkage on Page 255
  • Sample program is on Page 257
  • Called whenever a condition is not handled in the
    program
  • Displays error to user and terminates

48
LINKAGE SECTION
  • Used to access data left by previous execution of
    a program
  • Data should be moved to your W/S!
  • Each execution starts with initial W/S
  • Define COMMAREA in Working-Storage
  • DEFINE DFHCOMMAREA in Linkage
  • RETURN references Working-Storage

49
Executive Interface Block
  • EIB definition added by CICS Compiler
  • In Linkage Section after DFHCOMMAREA
  • Contains several useful fields
  • EIBCALEN, EIBAID, EIBCPOSN, EIBDATE, EIBTIME,
    EIBTRNID, EIBTRMID, EIBRSRCE
  • Most kept current by CICS (Page 258)
  • You can update a few of them-EIBTRNID

50
EIB Useful Fields
  • EIBCALEN Length of COMMAREA
  • EIBAID Current AID Key pressed
  • EIBCPOSN Position of CURSOR
  • EIBDATE Task DATE (00YYDDD)
  • EIBTIME Task Time (0HHMMSS)
  • EIBTRNID Transaction of Task
  • EIBTRMID Terminal ID of Task
  • EIBRSRCE Recently used Resource Name
  • EIBDS Recently accessed Data Set

51
DEBUGGING EIB FIELDS
  • EIBFN Last CICS Command
  • EIBRESP Completion Status
  • EIBRESP2 More Completion Status
  • EIBRCODE Response Code (OLD)
  • EIBRSRCE Recent Resource Name
  • MAP Map Name
  • PRG CTL Program Name
  • FILE CTL Data Set Name

52
Access to Heavy Stuff
  • CWA Common Work Area
  • Installation defined (Sometimes handy)
  • CSA Common System Area
  • TWA Transaction Work Area
  • TCTUA Terminal Control Table User Area
  • Must establish Addressability if needed

53
Infrequently Needed Stuff
  • EXEC CICS
  • ADDRESS CWA(pointer)
  • CSA(pointer)
  • TWA(pointer)
  • TCTUA(pointer)
  • END-EXEC

54
Infrequently Needed Stuff
  • EXEC CICS
  • ADDRESS CWA(ADDRESS OF CWA)
  • END-EXEC
  • NOTE Holdovers from MACRO-Level CICS
  • Seldom needed any more!
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