"DB2 CICS Interface" (PowerPoint 0.5 MB)

Information Management

Computer Consultant Company

DB2 / CICS InterfaceA View of the Interface between DB2/CICS

Patricia Townsend,Computer Consultant Company

[email protected]


Computer Consultant Company2

Agenda

Overview of CICS Program Flow

Review of CICS / DB2 Options

Review DB2 thread management concepts

Review DB2 BIND Options - Packages

CICS/DB2 Thread – Reuse Benefits

Evaluate Thread Reuse



Overview of CICS Program Flow

CICS Program Flow options– Start a CICS transaction – executed a CICS program– Program executes SQL which requires a DB2 DBRM– Program wants to XCTL or LINK to another CICS program– CICS linkage switches control to new program– At termination, each CICS program returns control

CICS Return– CICS returns control to next higher level program

Error Handling Processing– Each program level executes error handling routines– Control is given to next higher level program

Abend processing – Each program level executes abend routines– Control is given to next higher level program– DB2 UOW is managed with CICS UOW– CICS controls DB2 back out as required



Review CICS relating to DB2 using Threads

DB2 communicates to batch and on-line regions through use of threads.

– Threads are made up of control blocks that anchor the request to the requestor

– Batch acquires/releases threads according to program BIND

– CICS also acquires/ releases based on BIND options and CICS specifications

CICS provides for PROTECTED threads which are re-usuable.

A PROTECTED thread remains available for reuse based on CICS parameter settings.

Thread reuse saves CPU overhead to create/tear down.

Reduced CPU utilization is a benefit of thread reuse.



CICS Program Flow – Typical Mix Some w/DB2 / Some not

CICS programs ‘Go to’ any other CICS program

DB2 requires a DBRMCICS mainProgram

Tranid: ABCD

PgmANo DB2

PgmB DB2 SQL

PgmBBDB2 SQL

PgmCDB2 SQL

PgmDNo SQL



CICS Program Flow continued

Transaction ‘ABCD’ starts at Main CICS program.

Based on program options, from MAIN flows to PGMA, PGMB, PGMC or PGMD

– The CICS program does not need DB2.

– If DB2 is present, must have a DBRM

PGMB, PGMBB, and PGMC have DB2 content

– The BIND controls how the DBRM is identified

– Several options exist to find the DBRM



Review of CICS/DB2 Interface Options

CICS defines the DB2 Environment

CICS names the DB2 system

CICS defines the DB2 Interface

– Define TOTAL NUMBER OF DB2 THREADS

– Define How DB2 threads will be used

• By TRANID• By group of TRANIDs, etc.

– If a Thread will be PROTECTED

– If a Thread will be initialized at start up

– Duration of thread WAIT for reuse



Review of CICS/DB2 Options continued

Evaluate CICS/DB2 Interface options

– Thread define

– Protected Thread Allocation

– Threads at initialization

Evaluate DB2 BIND options

– Option 1 – The BIG Plan

– Option 2 – Dynamic Plan Selection

– Option 3 - Packages



Review CICS/DB2 Conventions

DB2 executes against a Thread

– The thread represents control blocks required to anchor DB2 activity

The DB2 UOW is managed by BIND variables

BIND ACQUIRE indicates when a thread is built

– At program initialization

– At first SQL use

BIND RELEASE indicates when a thread is available for teardown or reuse

– BIND DEALLOCATE – teardown thread when program is deallocated.

– BIND COMMIT – teardown thread when commit changes.



Review CICS/DB2 BIND options

The DB2 BIND options

– Option 1 - We can have ‘one BIG plan’ called ‘ABCD’ that all of the programs with DB2 are bound into….

– Option 2 - We can have separate plans for each program that has DB2 content, i.e. PGMB, PGMBB, and PGMC• The programs would use the DPS exit to load the proper DBRM• The program would do a sync point before issuing the CICS EXTL

or LINK to new program• The default exit would load the DBRM corresponding to the

program name

– Option 3 - We would bind each DB2 content program as a ‘package’. The 3 packages (PGMB, PGMBB, and PBMC) would be bound into a plan called ‘ABCD’.



Option 1 – The BIG Plan. Bind all DB2 programs into a PLAN Thread reuse

– One thread is acquired and used for the duration of the CICS TRANID execution.

Locking concurrency– Highest level of locking in any of the programs is propagated

for ALL programs using DB2.

– If a program is read only, but another UPDATES, the lock intent is UPDATE.

Plan change– To update any program, requires stopping ALL programs to do

the BIND and new copy ALL CICS programs.

– BIND requires re-binding ALL DBRMs used by ALL programs.



Option 2 – DPS (Dynamic Plan Selection) changes plan. Exit Drives new DBRM that matches program name

Thread Reuse

– No thread reuse.

– When execute SQL in program build thread. Sync Point drives exit leaving program forces thread tear down.

Locking Concurrency

– Lock granularity by program.

– Separate UOW for each program. Does not guarantee locks between program execution.

Plan Change

– Can individually change program/DBRM and re-BIND plan.

– Must Stop PROGRAM/PLAN to update.



Option 3 - Bind Package Benefits – Reduce Bind time

Before packages

– Program modification (with or without SQL change), required a BIND PLAN ACTION(REPLACE). This resulted in re-optimizing all DBRMs in the plan, even unmodified DBRMs. • This caused excessive resource and time consumption

• Undesired access path change for the unmodified DBRMs.

• Long outages during BIND

Solution Bind Package

- BIND PACKAGE allows a single DBRM to be optimized. If program changes, the package associated with it is the only package that needs to be rebound.

- None of the PLANS that contain this package need to be rebound.



DB2/CICS Interface – Define DB2 within CICS CICS defines DB2 Interface controlling DB2 thread management CEMT I

STATUS: ENTER ONE OF THE FOLLOWING OR HIT ENTER FOR DEFAULT

AUTInstmodel DSName JVMPool TCPIP

AUTOinstall DUmpds Line TCPIPService

AUXtrace ENQ MODename TDqueue

BEan ENQModel MONitor TErminal

BRfacility EXci Netname TRAnsaction

CFdtpool FEConnection PArtner TRDumpcode

CLasscache FENode PROCesstype TSModel

CONnection FEPOol PROFile TSPool

CORbaserver FEPRopset PROGram TSQueue

DB2Conn FETarget REquestmodel UOW

DB2Entry FIle RRms UOWDsnfail

DB2Tran Gtftrace STAtistics UOWLink

DEletshipped INttrace STReamname Vtam



DB2 Connection – How DB2/CICS Communicate

I DB2C

STATUS: RESULTS - OVERTYPE TO MODIFY

Accountrec( Txid ) Planexitname( )

Authid( ) Priority( High )

Authtype( Sign ) Purgecyclem( 00 )

Comauthid( ) Purgecycles( 30 )

Comauthtype( Csign ) Resyncmember( )

Comthreadlim( 0001 ) Signid( CICSDVLA )

Comthreads(0000) Security( )

Connecterror( Sqlcode ) Standbymode( Reconnect )

Connectst( Connected ) Statsqueue( CSSL )

Db2groupid( ) Tcblimit( 0047 )

Db2id( DSNW ) Tcbs(0000)

Db2release(0810) Threaderror(Abend)

Drollback(Rollback) Threadlimit( 0010 )

Msgqueue1( CSMT ) Threads(0000)

Msgqueue2( ) Threadwait( Twait )

Msgqueue3( )

Nontermrel( Norelease )

Plan( DEFAULT )



DB2 Connection continued

Authtype (Sign)– How the connection thread will identify to CICS/CICS transactions

DB2id(DSND)– Name of the DB2 subsystem this CICS will communicate with

DB2release(810)

Purgecyclem(00)– Purgecycles(30)– How often CICS will check for unused threads and tear down old threads.

Tcblimit(0047)– Total count of TCB attaches allowed for this CICS

Threadlimit(0010) – Total number of concurrent threads this CICS can talk to

Threads(0000)– Threadwait(Twait)– If a thread is unavailable, what should the requestor do, ie WAIT, TERMINATE



DB2 Entry statementIndicates DB2/CICS thread management

I DB2ENTRY


Db2e(ADDB ) Txi Sig Ena Poo Hig Pro( 0000 ) Pth(0000)

Threadl( 0000 ) Threads(0000) Tpo Plan( CCADDB25 )

Db2e(ADIN ) Txi Sig Ena Poo Hig Pro( 0000 ) Pth(0000)

Threadl( 0002 ) Threads(0000) Tpo Plan( ADIN )

Db2e(ADMT ) Txi Sig Ena Poo Hig Pro( 0000 ) Pth(0000)

Threadl( 0000 ) Threads(0000) Tpo Plan( ADMT )

Db2e(ADRB ) Txi Sig Ena Poo Hig Pro( 0000 ) Pth(0000)

Threadl( 0000 ) Threads(0000) Tpo Plan( ADRB )

Db2e(AMCS ) Txi Sig Ena Poo Hig Pro( 0001 ) Pth(0000)

Threadl( 0003 ) Threads(0000) Tpo Plan( DAMSE2 )



DB2 Entry statement - continued

Review elements of ENTRY statement

Db2e(ABCD) – pertains to CICS transaction, ABCD. It identifies the following:– Will use the CICS SIGNON to identify the user AUTHID.– It is ENABLED vs UNENABLED.– Runs as a POOL thread vs individual thread– Executes HIGH priority vs Medium or LOW.– Identified count of the presently executing threads.

Threadl(0003)

Threads(0000)

Tpo PLAN( DP003) plan name



DB2 Entry Statement – continuedDisplay of thread options

I DB2ENTRY

RESULT - OVERTYPE TO MODIFY

Db2entry(DPIN)

Accountrec( Txid )

Authtype( Sign )

Enablestatus( Enabled )

Disabledact( Pool )

Priority( High )

Protectnum( 0000 )

Pthreads(0000)

Threadlimit( 0002 )

Threads(0000)

Threadwait( Tpool )

Plan( APIN )

Planexitname( )

Authid( )

Drollback(Rollback) SYSID=DVLA APPLID=CICSDVLA

TIME: 10.11.41 DATE: 03.19.07



DB2 TRAN statement- Ties together CICS and DB2 information.

I DB2TRAN


Db2t(AADB ) Db2e( DADB ) Tra( DADB ) Plan(CdasDB25)

Db2t(APIN ) Db2e( DPIN ) Tra( DPIN ) Plan(DPIN )

Db2t(APMT ) Db2e( DPMT ) Tra( DPMT ) Plan(DPMT )

Db2t(APRB ) Db2e( DPRB ) Tra( DPRB ) Plan(DPRB )

Db2t(ASYN ) Db2e( DSYN ) Tra( DSYN ) Plan(DSYN )

Db2t(BMSP ) Db2e( BMPS ) Tra( BMSP ) Plan(BMPS )

Db2t(DGCS ) Db2e( DGCS ) Tra( WDOC ) Plan(CDMSE2 )

Db2t(DIAL ) Db2e( DIAL ) Tra( DIAL ) Plan(DIAL )

Db2t(DM01 ) Db2e( DT01 ) Tra( DT01,DT11 ) Plan(DT01 )



DB2 TRAN statement - continued

The TRAN statement identifies information to tie together CICS and DB2.

CICS transaction nameDb2t(DPIN )

DB2 entry thread name DB2e(DPIN )

DB2 PLAN that they will execute under. Plan(DPIN )



DB2 TRAN statement - continued

DB2 TRAN detail shows the following:

I DB2TRAN

RESULT - OVERTYPE TO MODIFY

Db2tran(DPIN)

Db2entry( DPIN )

Transid( DPIN )

Plan(DPIN)

Planexitname() plan exit other than DEFAULT MUST put name in Planexitname(xx) parm



Combining DB2 / CICS program requirements

CICS program compiled in load library

– This creates an executable object module with CICS code

DB2 requires a program with SQL be BOUND

– The BIND process creates a DB2 object module called a DBRM (Data Base Request Module)

– The DBRM h as the DB2 access path selection for going after the DB2 data requested in the SQL.

TO RUN, CICS object module / DB2 DBRM must MATCH

The PROCESS…..



Consistency Token used during package search

CT is embedded in modified source and DBRM at precompile time. It is propagated to the load module and package for integrity checking by DB2 at execution time.

The CT is a DB2 internal time stamp embedded to ensure package uniqueness to maintain the integrity of the executing load module and package.

Db2 Directory (SKPT01)

Packages

LOC1.COL1.PROGAV_ID

CT:1111

LOC1.COL1.PROGAV_ID

CT: 2222

Load Library

Load modules

PROGAV_ID: V1R1

CT: 1111

PROGAV_ID: V2R1

CT:2222



Binding packages

1. When PGMB is modified…

Action:BIND PACKAGE(COL1) MEMBER(PGMB) ACTION(REPLACE)

2. No need to bind PLAN1 and PLAN2

Packages can be used in more than one plan. To change PGMB, you BIND only that program/DBRM.

DBRMPGMA

DBRMPGMB

DBRMPGMC

PackageCOL1.PGMA

PLAN1

PackageCOL1.PGMB

PackageCOL1.PGMC

PLAN2



Using a PACKAGE LIST (PKLIST)

PLAN1- Bind only DBRMs BIND PLAN(PLAN1)

MEMBER(DBRMA,DBRMB)….

PLAN2 –Bound with both DBRMs

and packagesBIND PLAN(PLAN2)

MEMBER(DBRMA,DBRMB,DBRMC) PKLIST(COL.PACKA,COL.PACKB)…

PLAN3 – Bound only from packagesBIND PLAN(PLAN3)

PKLIST(COL.PACKB, COL.PACKC)…

One plan can include multiple DBRMs and multiple packages. One DBRM or one package can be included in multiple plans.

DBRMA

DBRMC

PLAN1

PLAN2

PLAN3

DBRMB

PACKA

PACKB

PACKC



Components of a Package Name

A package has a three-part name:Location_nameCollection_idPackage_id

Location_name.collection_id.package_id

DB2M.COL1.PROGA

DB2M.COL2.PROGB

PackagePROGA

PackagePROGB

COL1 COL2

PackagePROGB

BIND PACKAGE(COL1)

MEMBER(PROGA)

BIND PACKAGE(COL1)

MEMBER(PROGB)

BIND PACKAGE(COL2) MEMBER(PROGB)



Using an Asterisk in Package List (PKLIST)

Option: Meaning

•For Location_name

•(*.col1.pack1)

Location_name must be supplied at run time

CURRENT SERVER is set with:

SQL CONNECT statement in program

CURRENTSERVER option when bind plan

Default location DB2 loc name or blank if local DB2 has no location name



Using an Asterisk in PKLIST continued

Option: Meaning

•For collection_id

•(*.pack1)

Collection_id must be supplied at run time by:

CURRENT PACKAGESET special register

w/SET CURRENT PACKAGESET in program

DEFAULT IS BLANK

* For package_id (col1.*) All packages within specified collection are included



CICS / DB2 Verification of Thread Reuse

Evaluate Thread usage through

– Monitors

– CICS Shut down statistics– See DB2 stats:

> DB2 Connection> DB2 Entry> DB2 Performance



CICS / DB2 Shutdown Statistics DB2 CONNECTION STATISTICS

DB2 Connection Name . . . . . . . . . . . . : BB1P2

DB2 Sysid . . . . . . . . . . . . . . . . . : DB2W

TCB Limit . . . . . . . . . . . . . . . . . : 100

Peak number of tasks on the TCB Readyq. . . : 0

Pool Thread Plan name . . . . . . . . . . . :

Pool Thread Dynamic Planexit name . . . . . : DSNCUEXT

Pool Thread Authtype. . . . . . . . . . . . : USERID

Pool Thread Accountrec setting. . . . . . . : TXID

Pool Thread Threadwait setting. . . . . . . : YES

Pool Thread Priority. . . . . . . . . . . . : EQUAL

Total number of calls using Pool Threads. . : 8,455,563

Total number of Pool Thread Signons . . . . : 79,006

Total number of Pool Thread Partial Signons : 73,242

Total number of Pool Thread Commits . . . . : 10,085

Total number of Pool Thread Aborts. . . . . : 20

Total number of Pool Thread Single Phases . : 148,251

Total number of Pool Thread Reuses. . . . . : 0

Total number of Pool Thread Terminates. . . : 372,364

Total number of Pool Thread Waits . . . . . : 0

Pool Thread Limit . . . . . . . . . . . . . : 65

Peak number of Pool Threads in use. . . . . : 13

Peak number of Pool tasks . . . . . . . . . : 12

Total number of Pool tasks. . . . . . . . . : 113,156

Peak number of tasks on the Pool Readyq . . : 0

Command Thread Authtype . . . . . . . . . . : OPID

Total number of Command Thread Calls. . . . : 0

Total number of Command Thread Signons. . . : 0

Total number of Command Thread Terminates . : 0

Total number of Command Thread Overflows. . : 0

Command Thread Limit. . . . . . . . . . . . : 1

Peak number of Command Threads. . . . . . . : 0



CICS / DB2 Shutdown Statistics – DB2 ENTRY

DB2ENTRY STATISTICS - REQUESTS

DB2Entry Call Signon Partial Commit Abort Single Thread

Name Count Count Signon Count Count Phase Reuse

AADB 1 1 1 0 1 0 0

DYNAMIC 5088291 1637 84 0 0 213747 0

MCMHG000 45 5 3 0 0 5 0

MCMHH000 80 5 2 0 0 5 0

MCMHI000 11 2 0 0 0 6 0

MCMHP000 156 3 2 0 0 6 0

MCMHR000 69 3 0 0 0 4 0

MSSCC000 9631531 0 0 3341 1 5414 8724

MOSN 13364 119 109 36 0 198 0

NIPW 126M 0 0 0 0 3659034 3657871

*TOTALS* 142M 1775 201 3377 2 3881985 3670044

thread reuse



CICS / DB2 Shutdown Statistics – DB2 Performance

DB2ENTRY STATISTICS - PERFORMANCE

DB2Entry Thread Thread Pthread Pthread Task Task Readyq

Name Limit HWM Limit HWM HWM Total HWM

MCMHZ000 0 0 0 0 0 0 0

MSGBE000 10 3 5 3 3 1,588 0

MSSCC000 10 1 5 1 1 8,756 0

MSSCS000 0 0 0 0 0 0 0

MMSCY000 0 0 0 0 0 0 0

MOSN 0 0 0 0 1 234 0

NIPW 45 40 35 35 40 278,803 0

NSP1 0 0 0 0 0 0 0

*TOTALS* 502,578

See information on threads…

…limit, High Water Mark, Protected



References

IBM Redbook, “DB2 Packages: Implementation and Use”, GG24-4001-007083-00, October 1993

– http://publib-b.boulder.ibm.com/abstracts/gg244001.html

IBM ITSO San Jose Center, “CICS/ESA-DB2 Interface Guide”;

SG24-4536, September 1995

– http://publib-b.boulder.ibm.com/abstrcts/sg244536.html

“CICS/ESA System Programmer’s Guide” defines parms

– http://www-


Computer Consultant Company

Summary – Performance Benefits using Packages

Patricia TownsendComputer Consultant [email protected]

"DB2 CICS Interface" (PowerPoint 0.5 MB)

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