cm016g06

Course materials may not be reproduced in whole or in part without the prior written permission of IBM. 5.1

© Copyright IBM Corporation 2008

IMS Transaction Message Processing

Unit 6


Objectives

• Discover the message flow from terminals through IMS/TM or EMH to an MPR and how application programs (MPPs) are scheduled

• Discover the components and flow of MPPs (message processing programs)

• Learn a little about the macros that define MPPs to IMS/TM• Differentiate BMPs from MPPs and learn about extended

checkpoints and restart• Learn some of the implications of APPC• Identify the functions of OTMA (Open Transaction Manager

Access) and IMS Connect


User Terminal

z/OS

VTAM IMS/ MPR

IMS/ MPR

IMS/ BMP

IMS/ IFP

MSG

IMS/TM

Receive Task

Scheduler Task

Queue Manager

Expedited Message Handler

APPL

........................

APPL

........................

APPL

........................

APPL

........................

Message Queue

IMS DB(s)

IMS/TM Message Flow


001

002

003

SKILLINQ (8)SKILLUPD (5)PAYROLL (4)

INVENT (10)STOKSTAT (8)

ORDER (6)RECEIVE (4)

CLASSES TRANSACTIONS (PRTY)

Message Classes and Priorities

• TRANSACTIONS are assigned two (2) attributes:– Class, and– Priority

– Transactions are "grouped by" priority within class...– Class and priority can be changed via /ASSIGN command


IMS MESSAGE-QUEUE

SKILLINQCLASS=1, PRTY=8

MESSAGE 1

MESSAGE N

SKILLUPDCLASS=1, PRTY=5

MESSAGE 1

MESSAGE M

IMS/MPR1

IMS/MPR2

IMS/MPR3

Classes2,3,4,1

Classes3,4,5,6

Classes4,5,6,7

IMS S

CH

ED

ULE

R T

ASK

Message "Scheduling"

• Application programs are automatically scheduled only into– Message Processing Regions (MPRs)– Driven by occurrences of "messages"...


Control Region Message Region 1

INPUT MESSAGE

DATABASE(S)

OUTPUT MESSAGE

GET MESSAGE . . . . . . . . .ACCESS DB . . . . . . . . .INSERT REPLYGET NEXT MSGTERMINATE

Application Program: . . .

// EXEC PGM=DFSRRC00, PARM='MSG,002003004001...'

Scheduled Transaction Flow


COBOL Coding Example

READ THE INCOMING MESSAGE:CALL 'CBLTDLI' USING GU, IOPCB, IO-AREA

CHECK THE STATUS CODE:

IF STATUS-CODE = 'QC' END THE PROGRAM - OUT OF MESSAGES

HANDLE THE REQUEST:BLAH, BLAH, BLAH.

SEND THE REPLY

CALL 'CBLTDLI' USING ISRT, IOPCB, IO-AREA.

LOOP TO THE TOP TO GET THE NEXT MESSAGE.


IMS MESSAGE-QUEUE

SKILLINQCLASS=1,PRTY=(8,10,30)PROCLIM =20

MESSAGE 1

MESSAGE N

SKILLUPDCLASS=1,PRTY=(9,12,4)PROCLIM=5

MESSAGE 1

MESSAGE 2

MESSAGE M

NORMAL PRIORITY

LIMIT PRIORITY

LIMIT COUNT

QUEUE COUNT

NORMAL PRIORITY

LIMIT PRIORITY

LIMIT COUNT

QUEUE COUNT

TIME 1 TIME 2 TIME 3

912 4 2

912 4 1

9 12 4 3

10

30

0

10

30

8

10

30

30

88 8

Message Queue "Limit Priority"

• Additional factors affecting scheduling


Message Region Options

• More scheduling options

• "Wait-For-Input (WFI)" transactions:– Allows a program to remain scheduled to wait for the next

transaction, subject to PROCLIM=• Parallel-scheduling:

– Allows the same program to be scheduled in parallel address-spaces at the same time• IF processing a different transaction code• Subject to queue-count of each transaction code Upper limit maximum

• Preload of application programs into certain regions– Program is "ready and waiting" when application schedules


Dynamic Transaction Backout

• When the program reads the incoming message:– Call 'CBTDLI' using GU, IOPCB...

• All updates and messages for the previous transaction are committed.

ABEND

• Dynamic transaction backout is invoked automatically when a program abends.

• Any uncommitted updates or messages are purged when a program abends.

• Any uncommitted updates or messages are purged from the system.


APPLCTN PSB=INQPGM,PGMTYPE=(TP,,1) Class

TRANSACT CODE=SKILLINQ,PRTY=(8,10,20),PROCLIM=20

APPLCTN PSB=UPDPGM,PGMTYPE=(TP,,1) Class

TRANSACT CODE=SKILLUPD,PRTY=(5,12,4),

PROCLIM=5

TRANSACT CODE=SKILLDLT, PRTY=(6,9,20)

APPLCTN PSB=ORDPGM,PGMTYPE=(TP,,4) Class

TRANSACT CODE=ORDERENT, PRTY=(8,12,4), SPA=(200)

APPLCTN PSB=BILLPGM,PGMTYPE=(TP,,7) Class

TRANSACT CODE=BILLING, PRTY=(12,14,5),

SPA=(200)

IMS GEN - Message Processing


SKILLINQ XXX

INVENTUP XXX

RESULTS

IMS/TMControlRegion

1 MESSAGE QUEUED

2 IMSMPR2 AVAILABLE IMSMPR1 AVAILABLE

3 CONTROL BLOCKS LOADED HERE...

IMS/MPR1 IMS/MPR2(Class 2,3,4,1)

(Class 4,5,6,7)

z/OS

4. INQPGM LOADED, EXECUTION BEGINS HERE...5. GET MESSAGE FROM QUEUE...6. GET DB SEGMENTS FOR INQUIRY...7. INSERT MESSAGE REPLY BACK TO THE QUEUE8. TERMINATE

THIS REGION WAITING FOR

WORK

9. SEND MESSAGE FROM QUEUE TO TERMINAL

LTERMSF101

PGMLIB

INQPGMUPDPGM

INVPGMVENPGM

PGMLIB

SKILLNQ123456

SKILLINQRESULTS SCREEN

Message Processing Programs (MPPs)


FUNCTION PCB CODE

RETRIEVING MESSAGES: GET UNIQUE GET NEXT

IO-PCBIO-PCB

GUbbGNbb

SENDING MESSAGES to ORIGINATING TERMINAL: INSERT IO-PCB ISRT

SENDING MESSAGES to ALTERNATE TERMINALS: CHANGE INSERT PURGE

ALT-PCBALT-PCBALT-PCB

CHNGISRTPURG

CHECKPOINTING of the BATCH APPLICATION: CHECKPOINT SYNC-POINT

IO-PCBIO-PCB

CHKPSYNC

Message Processing Calls


SCRATCH-PAD AREA

'ORDPGM'PROGRAM

'ORDPGM'PROGRAM

'ORDPGM'PROGRAM

SCRATCH-PAD AREA

SCRATCH-PAD AREA

ORDERENT 00000000000000000000000000000000

ORDERENT DOE,J12-3456 00000000000000000000

ORDERENT DOE, J12-3456 9876550 BLUE 75 RED

ORDERENT DOE,J12-3456 00000000000000000000

ORDERENT

ORDERENT DOE, J12-3456 00000050 BLUE 75 RED

BBBBBBBB DOE, J12-3456 9876550 BLUE 75 RED

BEFORE

BEFORE

BEFORE

AFTER

AFTER

AFTER

NAME: JOHN DOEADDR: 123 MAIN CHICAGO ZIP: 60601ACCT: 12-3456

ORDER; 98765ITEM QTY DESC1 50 BLUE2 75 RED3

ORDER: 98765PRICE: 50.00TAX : 5.00TOTAL: 55.00 ORDER COMPLETE

Conversational Processing


Batch Message Processing (BMP) (1 of 2)

• Programs are "batch" programs– Submitted when ready by Operations

• May or may not access the message queue:– 1. Transaction oriented BMP: processes input messages and inserts

output reply• BMP address-space JCL parameters (IN= , OUT=)

– 2. Non-transaction oriented BMP: access databases only

• IMSGENAPPLCTN PSB=HQPGM,

PGMTYPE=(BATCH)

TRANSACT CODE=HQUPDT, PRTY=(0)

APPLCTN PSB=DB2PGM,PGMTYPE=(BATCH)


Control Region

DATABASE(S)

Batch Message Region

Application Program:. . .. . .

READ z/OSDATA SET

. . .. . .

ACCESS DB(S). . . . . .

CALL 'CHKP'GET NEXT I/PTERMINATE

// EXEC PGM=DFSRRC00, PARM='BMP,PGMNAME,PSB,...'

Batch Message Processing (BMP) (2 of 2)

• Non-Transaction Oriented BMP


• APPC is the most commonly used SNA protocol when accessing IMS from a CGI program– Conversational Model– APPC Supports

• Asynchronous• Synchronous

– interactive

CGI Pgm IMS

SNAAPPC Calls

APPC Calls

GU...ISRT

CGI Pgm IMS

SNAAPPC Calls

scheduling

APPC Calls

IMS appl pgm

Standard CPIC Driven

...SENDRCV...

RCV...SEND

APPC


IMS

CONTROL MPPREGION RECEIVE

. . . SEND-DATA request CONFIRM

APPC/MVS

LU 6.2DEVICE

APPC/VTAM

VTAM BASE

IMS APPC Explicit API Flow


APPC Support

• APSB (allocate PSB) call– Dynamically allocate a PSB– CPIC driven programs have no access to a PSB when scheduled– Allows access to IMS resources when application is CPIC driven

• DL/I data bases• Alternate PCB output

• All transaction modes supported for current and modified programs– Conversational– Response– Non-response


IMS Data Comm.

APPC Comm. (Using XCF)

Open Transaction Manager Access (OTMA)

OTMA and OTMA Callable Interface

• IMS Component providing enhanced access to IMS from middleware

SNA Network TCP/IP MQSeries DCE/RPC WebSphere TCP/IP Client

Common Interface (XCF)OTMA Callable

Interface

Transaction Manager IMS Message

Queues

IMS

TM

Appl. Appl. Appl.. . .

DB2 IMS Database Manager

Open DB Access Facility


z/OS

TCP/IP for z/OS

IMS Connect(BPE)

IMS

TRAN

DATA

OTMA XCF

User Exit

User Exit

WebSphere

IMS Connector for Java

IMS TCP/IP Client

TCP/IP

TCP/IP OTMA Connection

• Provides improved access via TCP/IP


Back-end Services (IMS)

z/OS

IMS Connect

IMS

OTMA

IMS Application Programs

Java Applicationusing

IMS Connector for Java

XCF

TCP/IP

Internet

IMS Connect


Unit Summary

• Transactions are scheduled as a function of matching classes defined in MPR JCL with the class (CLASS) and priority (PRTY, PROCLIM) assigned to a transaction in an IMSGEN

• Message processing programs (MPPs) receive messages from terminals by issuing get calls (GU and GN) and return messages with insert calls (ISRT) to an I/O PCB

• Application transactions are defined in an IMSGEN using APPLCTN and TRANSACT macros

• BMPs execute during online processing and should also have checkpoint and restart logic

• APPC programs can contain dynamic allocations of PCBs and are scheduled by IMS, however, other IMS/TM communication processes are bypassed

• OTMA provides the facility for IMS to communicate with IMS applications other than VTAM, such as TCP/IP

• IMS Connect provides enhanced TCP/IP support for easy access to IMS from the Internet

cm016g06

Documents

incoming message

message nskillupdclass

message classes

previous transaction

program abends

application programs

status code

access db