IMS Fundamentals - Transaction Manager

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 Manager

Unit 5


Objectives

• Understand the goals and architecture of IMS/TM (Transaction Management)

• Learn the LTERM concept and how it relates to messages, message types and queues

• Learn how IMSGEN control blocks required for TM are coded and maintained

• Know the how IMSGEN control blocks, PSB and MFS control blocks are used in TM

• Understand the Master Terminal Operator and IMS terminal commands

• Understand IMS system security, integrity and maintenance functions


z/OS

IMS/BATCHAddress Space

Application

DL/I Modules

Data Buffers



Application

DL/I Modules

Data Buffers

Application

DL/I Modules

Data Buffers

Database

(C)

Database

(A)

System

Log

Database

(B)

System

Log

System

Log

Multiple IMS Batch Address Spaces


Goals of IMS/TM

• Provide high-volume, rapid response transaction management processing for application programs accessing– IMS/DB database (full function and Fast Path)– DB2 tables

• Define a logical/physical terminal structure that supports– Growth– Change independence– Usage of common resources– Productivity

• Support database management integration– Data integrity through two phase commit of unit of work– Reliability/availability/serviceability (RAS) through

transaction/database logging


ONLINE LOG DATA SET

CORPORATEDATABASESRECON MSG

QUEUE

z/OS

IMSCTL Control Region

MESSAGESCHEDULING

LOGGING/ RESTART

DBRCRecover

y Control

DLISASDL/I

SubordinateAddress Space

MPRMessageProcessin

gRegion

BMPBatch

MessageProcessin

g

IFP Fast Path

Region

TELECOMMUN- ICATIONS

LOGCTL

DL/I ACTION

MODULES

APPL PGM

APPL PGM

APPL PGM

USERTERMINA LS

IMS/TM makes data available to the end-user...

MASTERTERMINA L

IMS/TM Architecture


IMS/TM Dependent Regions• Maximum of 4095 dependent regions

– Message Processing Regions (MPRs):• Selective start-up at IMS initialization• Processes "online" transactions from terminals• IMSCTL automatically "schedules" application programs for execution to

process IMS/DB databases, or DB2 tables• Many different application programs can process in a given MPR

throughout processing period

– Batch Message Processing (BMP) regions:• Started when JOB submitted by operations• Runs one application-program to process queued transactions, IMS/DB

databases, and/or z/OS files• Allows batch-type programs to process IMS queues and databases while

IMS/TM system is available

– Interactive Fast Path (IFP) regions:• Bypass IMS/TM scheduling via Expedited Message Handler (EMH)• For large transaction volumes that require fast response


IMSCTL (Control Region)DATA COMMUNICATIONS:

MPR(Msg. Processing Region)

LOGICAL TERMINAL

ABC

MESSAGES

APPLICATION PROGRAM

'ANYPGM'

LOGICAL TERMINAL

XYZ

PHYSICAL TERMINAL

1

PHYSICAL TERMINAL

2

PHYSICALTERMINAL 3

Logical Terminal (LTERM) Concept


• Transactions

– Originate from terminal (most IMS/TM activity)– Can originate from another application-program via "program-switch"

• Message-switches

– Allows terminals to communicate with each other

• Commands

– Mostly entered by MTO– Some commands may be entered from user terminals

/ COMMAND-VERB (PASSWORD) text 1 2 n

LTERMnme (PASSWORD) text1 8 9 18 19 n

TRANcode (PASSWORD) text1 8 9 18 19 n

Message Types


Message Type Examples• Transactions:

– SALARY(XPSWD) 123456'Salary for John Doe (123456) is $xxx.xx'

– ADDINV PART 9876 QTY=50'Inventory on 9876: 10-Speed Bicycle = 9950 units'

• Message-Switches– ACTGTERM

ACCOUNTING DEPARTMENT MEETING AT 2:00PM

• Commands

/checkpoint freeze

/start line 5 pterm 2

/change(zzzyyx) password 999888 to password 888999


z/OS

All INPUT and OUTPUT messages are queued...

MESSAGE QUEUE

DATA SET(S)

IMS/TM IMS/MPR1 IMS/MPR2

QUEUEBUFFERS

QUEUEMANAGER

GET FROM

QUEUE

INSERT

TO QUEUE

A P P L

GET FROM QUEUE

INSERTTO QUEUE

A P P L

. . . .

. .. . . . . .

Message Queue (1 of 2)LOGICAL

TERMINAL(LTERM)


TRAN X

TRAN Y

1. INPUT TRANSACTIONS are QUEUEd by:

MSG1 (LTERMA) X

MSG3 (LTERMX) X

MSG4 (LTERMQ) X

MSG7 (LTERMX) X

MSG2 (LTERMB) Y

MSG5 (LTERMZ) Y

MSG6 (LTERMA) Y

2. OUTPUT MESSAGES are QUEUEd by:

LTERMA

LTERMB

RPL1 (X)RPL3 (X)

RPL2 (Y)

MESSAGE-QUEUE BUFFERS (Control Region)

MSG1 RPL3 RPL2 MSG5 MSG7RPL1 MSG6

MSG2 MSG4 MSG3

MESSAGE QUEUEDATA SET(S)

Message Queue (2 of 2)


PSBs for IMS Transaction Manager

PCB TYPE=TP

PCB TYPE=DB

PSBGEN...

• TP– Alternate response IOPCB.

• Used to send a message.

• DB– Used to read or update a database - same as IMS db.


APPLICATION PROGRAM:

MASK

MASK

MASK

(TP-) IO- PCB

ALTIO-PCB

DATABASEPCB

LOGICALTERMINA L

ALTERNATELOGICAL

TERMINAL

CUSTOMER

ADDRESS PAYROLL

LOGICAL DATABASE STRUCTURE

LOGICALTERMINA L

LOGICAL TERMINA

L

Logical Structures


INVENTORY MENU 100

10

PART-NO: 200

INVPGM

INVENTORY ON-HAND :

100 99

200 789

10 1000

A. DEVICE INPUT FORMAT (DIF)

D. DEVICE OUTPUT FORMAT (DOF)

INVPGM 00100 00200 00010

B. MESSAGE INPUT DESCRIPTOR (MID) (EDITED MESSAGE)

C. MESSAGE OUTPUT DESCRIPTOR (MOD)(EDITED MESSAGE)

100 0099 200 0789 10 1000

APPL PGMISRT

NXT=

MODNAME

MES

SAG

E FO

RMAT

SER

VICE

S (M

FS)

Message Format Service (MFS)


PAYROLL MENU:NAME:____________SERIAL:___________ADDRESS:_________DEPT:_____________PF1=UPDTPF3=EXIT

/FORMAT PAYMENU

MFS – Formatting a Screen

• FORMATTING A SCREEN:– Using /FORMAT command:

• No program is involved– Using Program-control:

• Format screen using output message from a program• CALL 'CBLTDLI' USING ISRT IO-PCB IO-AREA PAYMENU

– Message that is written to queue contains MOD name to be used to map a DOF (screen-format) name


SF00 MSG TYPE=OUTPUT, SOR=(SFIL00, IGNORE), OPT=2,NXT=SFIN00,FILL=PT

MFLD REPLY, LTH=50,JUST=L MFLD SKILL, LTH=8, JUST=L MFLD NAME,LTH=6, JUST=L MSGEND

Creates MOD...

SFIN00 MSG TYPE=INPUT,SOR=SFIL00,OPT=2, NXT=SF00

MFLD TRANCD,LTH=6,FILL=NULL MFLD TYPESEG,LTH=1,JUST=L, FILL=C' ' MFLD SNE, LTH=18,JUST=L, FILL=C' ' MFLD DEGREE, LTH=1, JUST=L, FILL=C' ' MFLD SUBJECT, LTH=15, JUST=L,FILL=C' ' MFLD CDATE,LTH=4, JUST=L,FILL=C' ' MSGEND

Creates MID...

MFS – Creating Control Blocks

• Creating MFS control blocks://TEST EXEC @MFS//SYSIN DD * PRINT NOGEN


Creates DIF/DOF...

MFS - Source

SFIL00 FMTSFIL00 DEV TYPE=(3270,2) ,FEAT=IGNORE, PFK=(TRANCD,'CONVA '), DSCA=X'00A0' DIV TYPE=INOUT DPAGE CURSOR=((5,7)) DFLD 'SKILL INVENTORY UPDATE',POS=(2,30),ATTR=(NUM,PROT,HI) DFLD 'TYPE',POS=(5,2), ATTR=(NUM,PROT,HI)TYPESEG DFLD POS=(5,7), LTH=1 DFLD 'SKILL/EMPLOYEE/COURSE',POS=(7,2),ATTR=(NUM,PROT,HI)SNE DFLD POS=(7,24),LTH=18 DFLD 'DEGREE',POS=(9,2),ATTR=(NUM,PROT,HI)DEGREE DFLD POS=(9,9),LTH=1 DFLD 'SUBJECT',POS=(11,2),ATTR=(NUM,PROT,HI)SUBJECT DFLD POS=(9,9),LTH=1 DFLD 'COMPLETION DATE',POS=(13,2),ATTR=( NUM,PROT,HI)CDATE DFLD POS=(13,18),LTH=4 DFLD 'CURRENT SKILL',POS=(15,2),ATTR=(NUM,PROT,HI)SKILL DFLD POS=(15,16),LTH=8 DFLD 'CURRENT NAME',POS=(15,25),ATTR=(NUM,PROT,HI)NAME DFLD POS=(15,39),LTH=6 DFLD 'RESULT',POS=(17,2),ATTR=(NUM,PROT,HI)REPLY DFLD POS=(17,9),LTH=50 DFLD 'USE PF KEY 1 TO BEGIN THE CONVERSATION',POS=(23,2) FMTENDEND/*


A system resources controller LTERM that is the operational "hub" of IMS/TM...

COMMUNICATIONS

COMMUNICATIONLINES/NODES

PHYSICAL TERMINALS

LOGICALTERMINALS

TRANSACTIONS AND

PROGRAMS

MESSAGE REGIONS

SYSTEMSTATUS

CHECKPOINT/ RESTART

DATABASE DUMP and

RECOVERY

z/OS system console is "back-up" to MTO console...

SCHEDULING INTEGRITY

LOGICALTERMINA L

MASTER TERMINAL

DATABASE(S)

Master Terminal Operator (MTO)


Terminal CommandsMASTER Terminal: REMOTE Terminal:

/NRESTART "Normal" /ERESTART "Emergency"/CHECKPOINT

/DISPLAY /SIGN ON USERID PAYROLL/ASSIGN /SIGNOFF/CHANGE /IAM LTERM PAYROLL/STOP and /START NODE /LOCK LTERM PAYROLL

DATABASE PROGRAM TRANSACTION REGION

/BROADCAST NODE ALL /HOLDPAYROLL DATABASE UNAVAILABLE /RELEASE CONV 004UNTIL 2:00PM /EXIT

/RMLIST DBRC='DB DBD(DIVNTZ04) DBDS' /FORMAT PAYMENU /TEST

/DBDUMP /EXCLUSIVE/DBRECOVERY /RDISPLAY MASTER

/OPNDST /RCLSDST/CLSDST/MODIFY PREPARE/MODIFY COMMIT


System Integrity Functions

• Common Logging Facility:– Database changes, transactions, system status changes

• Automatic system checkpoints– Based on system activity– System Recovery and Emergency Restart

• Database Recovery Control– Similar to batch recovery operations

• Program Isolation– Automatic backout for program ABENDs– Data Sharing by multiple programs

• Normal Restart– Start with unprocessed input/output from previous execution


OLDS5

OLDS4

OLDS3OLDS2

RECON 3

RECON 2

z/OS

IMS/TM

DBRC DLISASContro

l Region

DB Recovery Control

DL/I Subordinate Address Space

SLDS2

SLDS1

RLDS2

RLDS1

SYSTEM LOG DATA SETS

RECOVERY LOG DATA SETS

LOG ARCHIVE UTILITY

WADS

WRITE AHEAD DATA SETS

RECON 1

Buffers Buffers

OLDS1

Common Logging Facility


Common Logging Facility (Cont)

• Recording of IMS/DB and IMS/TM system activity:– "Before" and "After" images of changed DL/I segments– System status via periodic checkpoints– Input and Output messages are logged

• Provides integrity and recoverability of DB/TM systems:– Used for Dynamic Backout of failing transactions– Used for system "warm" and "emergency" restarts– Used for database recovery– Used for performance and accounting statistics

• Log Write-Ahead (LWA):– To guarantee database integrity, log records are physically written

before database physically written– Only selected "events" qualify for this technique


OLDS and WADS

• Online Log Data Set (OLDS)– Contains log records needed for:

• Restart • Recovery• Backout: Batch and Dynamic

– Consists of multiple data sets– Allows IMS/TM to continue logging when an "OLDS switch" occurs

because of the following:• OLDS is full• I/O error while writing to an OLDS• Operator commands /DBR or /DBD

– Written in a "wrap-around" manner– Can be archived automatically to the System Log Data Set (SLDS)

• Write Ahead Data Set (WADS):– Contains committed log records not yet written to OLDS

• Normally, only full blocks are written– May be used to "close" the OLDS in an emergency


Database Recovery Control (DBRC)• TWO LEVELS OF CONTROL:

– LOG-CONTROL, controller of IMS log data sets:• Maintains information about OLDS status

– e.g. ARCHIVE-NEEDED, AVAILABLE, ARCHIVE-IN-PROGRESS, NEXT-OLDS– 2a. SHARE-CONTROL since IMS 6.1 includes RECOVERY-

CONTROL functions of earlier releases• can assist in database integrity and recovery• Database "registration" by database data set• Monitors Database Image Copies (ICs), Change Accumulations (CAs), Recoveries

(DBRs)• Automatic JCL generation of needed job-streams

– 2b. SHARE-CONTROL enables database sharing:• Access-intent must be registered with a "share-level“

– Database-level sharing– Intra- or inter-processor block-level sharing

• There is no DBRC or IMS "parm" that determines Log-Control vs. Share Control– Share Control is in effect for individual databases once they are

"registered"


"The RECON" for Log-Control (1 of 2)

• Recovery Control Data Sets (RECON):• Automatic recording of information about:

– Online Log Data Set (OLDS)– System Log Data Set (SLDS)– Recovery Log Data Set (RLDS)

• Generation of utility JCL via DBRC command for:– Log Archive– Log Recovery


//DFSOLP00

//DFSOLP01

//DFSOLP02

OLDS 1

OLDS 3

STATUS: ARCHIVE SCHEDULED

STATUS: IN USE

STATUS: AVAILABLE

RECON

PRIOLD

SECOLD

PRISLD

SECSLD

PRILOG

SECLOG...

ARCHIVE

JOB:

ARC001SLDS1

RLDS1

OLDS 2

"The RECON" for Log-Control (2 of 2)


DBRC Database "Registration" for Share Control

• Advantages:– Records recovery-related information in RECON

• Example: which OLDS has log data for each database data set (DBDS) registered with DBRC

– Controls recovery of databases

– Generates JCL for recovery-related utilities• Used to select correct data sets to be used by Recovery and Image-Copy• Consolidates changes of log records• Saves time• Eliminates errors

• Register databases with DBRC commands – once a database is registered, Share Control is in effect


Restart CheckpointType: Selected:

COLD CHKPT 0

WARM CHKPT Generated At Previous Shutdown

EMERGENCY Last CHKPT Written to Log

Checkpoint and Restart (1 of 2)

• IMS uses its own CHECKPOINT processing• System-wide checkpoint is taken periodically based on

– volume of log-records generated• Restart is based on use of a CHECKPOINT which contains

– a "snapshot" of system control-blocks to log data set (OLDS)


z/OS

IMS/TM DBRC DLISAS

MESSAGEQUEUE(S)

RECON DATABASE(S)

Checkpoint and Restart (2 of 2)

1. z/OS System Failure2. Stand-alone dump3. Restart z/OS operating system4. Emergency Restart IMS:

– Database backout of "in-flight" transactions1. “In-flight" transactions re-scheduled2. Message queue reconstruction3. Message transmission repositioning

5. Continue processing


System

Application

Terminal Network

IMS Generation (IMSGEN)• IMSGEN MACROS

Macro Function

IMSCTRL System-wide parametersIMSCTF z/OS parametersMSGQUEUE Message Queue definitionsBUFPOOLS Control-block buffer-pools

DATABASE DatabasesAPPLCTN Applications/Programs (PSBs)TRANSACT Transactions

COMM Communications defaultsTERMINAL Physical TerminalsNAME Logical Terminals (LTERMs)

• Online Macro changes through Online Change facility– DATABASE– APPLCTN– TRANSACT– MFS format Block


Extended Terminal Option (ETO)

• Optional (additional cost) Feature of IMS/TM• Terminals may optionally be defined outside of the IMSGEN

Process.• Fewer IMSGENs• Smaller and faster IMSGENs • Dynamic control block management• Requires user sign on


Unit Summary

• IMS/TM supports the RAS (Reliability, Availability & Serviceability) characteristics for application transaction processing programs

• LTERMs isolate messages, message types, queues and program processes from physical terminal characteristics

• IMSGEN, PSB and MFS control blocks are used in different aspects of TM

• Master Terminal Operation capabilities and IMS terminal commands are available to control and maintain transaction systems

• IMS system security, integrity and maintenance functions exist• ETO and DRF are additional cost options/tools that extend the

capability of IMS

IMS Fundamentals - Transaction Manager

Technology

Transcript of IMS Fundamentals - Transaction Manager