Threadsafe by the book

© 2012 IBM Corporation

CICS Lunch n LearnThreadsafe by the Book(The Redbook)

Gary Andrews

Client Technical Specialist: CICS Tools

andrewga@us.ibm.com

The BookSG24-6351-0*

3

Agenda

Why Threadsafe

In The Beginning

Threadsafe Conversion Plan (and my Threadsafe experience)

Questions

Summary

4

Why Threadsafe?

Save CPUTake advantage of modern: Hardware Design Software Design.

In the Beginning Your applications were Sleek and

Fast

Then your applications became popular. Volume increased. You added new functionality. But response time started to decline. Users complained.

How did you fix this mess?

Many of us added hardware.

And we took advantage of multiple engines in the new mainframe hardware.However, we migrated from a simple design……..

CICS RegionApplications

To split regions due to Virtual Storage Constraint

CICS RegionApplication 2

CICS RegionApplication 1

CICS RegionApplication 3

And we added even more regions

Quality Assurance ProductionSystem Test

Development

Application 1

Application 2

Application 3

Application n

As of CICSTS V2.2You have a 3rd option

Open Transaction Environment (OTE)

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Let’s review the steps of a Threadsafe project

Indentify Exits

Indentify high cpu/high TCB switching transactions

Indentify the programs used by those transactions and review

Mark reviewed programs as Threadsafe (Concurrency=Required (V4.2 and V5.1)

Validate your work.

Indentify Exits• Global User Exits: Exec CICS Inquire Exitprograms

• Using Program DFH0STAT

Indentify Exits• Identify homegrown and vendor exits

Identify High CPU Transactions

Or Identify High TCB Switching Transactions

Now Let’s Identify the Programs Used by Our Target Transactions

After Review Change Concurrency of the Program to either Threadsafe (prior to V4.2) or Required (V4.2 and newer)

Now Let’s Verify Our Work (Part 1)

Now Let’s Verify Our Work (Part 2)

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QR TCB

L8 TCB

(1) (2) (1) (2)

CICS TS V4.1 Threadsafe CICSAPI

QR TCB

L8 TCB

(2) (3) (2) (3)

CICS TS V4.2 Threadsafe Required

CICS TS V5.1 Threadsafe RequiredL8 TCB

(1) Changemode due to DB2 call

(2) Changemode due to TD Write

(3) Changemode back to L8 due to Required option

What is Concurrency=Required?

If you did a Threadsafe Conversion Prior to CICSTS V4.2

• After you install V4.2 or V5.1

• Review your program definitions.

• Consider changing

• Concurrency=Threadsafe to

• Concurrency=Required

Consider This: Are these transactions Threadsafe Candidates?

What would happen if they were Threadsafe?

• No immediate CPU savings

• Greater throughput for important transactions

• Free up the QR TCB

• Opens the possibility of region consolidation.

• Region consolidation = CPU savings!!!

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SummaryThreadsafe Project Steps

Indentify Exits

Indentify high cpu/high TCB switching transactions

Indentify the programs used by those transactions and review

Mark reviewed programs as Threadsafe (Concurrency=Required (V4.2 and V5.1)

Validate your work.

You want to transition from this

QR TCB

TCB Switching

L8 TCB’sL8 TCB’s

To ThisAll Important Transactions do not switch off the L8 TCBs

L8 TCB’sL8 TCB’s L8 TCB’s

Find out more

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