Threadsafe Considerations for CICS - IBM Redbooks

1 Considerations for CICSC hris RaynsGeorge BognerPhilip HaleEm JamesPeter KleinJohn TillingNew Threadsafe options in cics Transaction Server for z/OS value of Threadsafe applications in a cics environmentCICS Tools to help migrate applications to be threadsafeFront coverThreadsafe Considerations for CICSA pril 2012 International Technical Support OrganizationSG24-6351-04 Copyright International Business Machines Corporation 2004, 2012. All rights to Government Users Restricted Rights -- Use, duplication or disclosure restricted by GSA ADPS chedule Contract with IBM edition (April 2012)This edition applies to cics Transaction Server for z/OS : Before using this information and the product it supports, read the information in Notices on page xi. Copyright IBM Corp. 2004, 2012. All rights .. xiTrademarks .. xiiPreface .. xiiiThe team who wrote this book .. xivNow you can become a published author, too! .. xvComments welcome .. xviStay connected to IBM Redbooks .

2 XviSummary of changes.. xviiApril 2012, Fifth Edition .. xviiNovember 2010, Fourth Edition .. xviiNovember 2007, Third Edition .. xviiiJuly 2006, Second Edition .. xviiiPart 1. Threadsafe concepts and definitions .. 1 Chapter 1. Introduction to cics open transaction environment.. The concept of the cics open transaction environment.. Improved throughput .. Improved performance .. cics data integrity for shared resources .. Quasi-reentrant and Threadsafe programs .. Shared application resources .. Shared cics resources .. Threadsafe applications .. Benefits of Threadsafe -enabled applications .. Improving performance .. Reducing the cost of computing .. Using OTE.. The importance of understanding your applications .. 10 Chapter 2. Overview of an open transaction environment and Threadsafe applications.. Overview of quasi-reentrant and Threadsafe programs .. Quasi-reentrant programs .. Threadsafe programs .. CICSAPI programs.

3 OPENAPI programs .. 15iv Threadsafe Considerations for Open transaction environment: A brief history .. Before cics Transaction Server .. cics Transaction Server .. cics Transaction Server .. cics Transaction Server .. cics Transaction Server .. cics Transaction Server .. cics Transaction Server .. Open TCB modes in cics Transaction Server V2 .. Open TCB modes in cics Transaction Server V3 and later .. Techniques to ensure Threadsafe processing .. Program definition .. Task-related user exit APIs .. cics DB2 task-related user exit .. cics IMS task-related user exit .. cics WebSphere MQ task-related user exit .. IP sockets task-related user exit .. TCB limits .. MAXOPENTCBS.. Open TCB performance .. DB2 .. IMS .. WebSphere MQ .. IP cics Sockets interface.. Performance Considerations .. TCB Considerations with UNIX System Services .. Implications of setting MAXPROCUSER too low.

4 Static and dynamic calls .. Threadsafe and nonthreadsafe commands in cics Transaction Server Threadsafe API commands.. Threadsafe SPI commands.. Threadsafe XPI commands.. Nonthreadsafe SPI commands .. Function shipping Considerations .. Before cics Transaction Server .. cics Transaction Server and later .. 52 Chapter 3. Threadsafe techniques.. Threadsafe standards .. Serialization techniques .. Recommended serialization techniques .. Generalized compare and swap routine .. Nonrecommended techniques .. 60 Contents Application design Considerations .. Application design Considerations for cics TS .. Application design Considerations for cics TS .. 64 Part 2. Threadsafe implementation.. 69 Chapter 4. Threadsafe tasks .. Threadsafe enablement planning .. cics Transaction Server upgrade and enablement path .. High-level Threadsafe enablement path .. Load module scanner: The DFHEISUP utility.

5 DFHEISUP filter tables .. DFHEISUP summary mode .. DFHEISUP detail mode .. DFHEISUP summary .. 81 Chapter 5. Application review .. Reviewing the application code .. Ensuring that the program logic is Threadsafe .. Example showing the use of shared resources .. Assembler data tables.. Ensuring usage of only Threadsafe cics commands .. Changing the program definitions .. Changing the RDO definition .. cics environment variable CICSVAR .. CICSVAR values .. Coding ENVAR .. Example of file control application.. 100 Chapter 6. System programmer tasks.. Role of the system programmer .. Understanding Threadsafe operation .. Threadsafe performance issues .. Threadsafe data integrity issues .. Analyzing the cics regions .. DB2 version.. WebSphere MQ version .. IMS version .. DB2 system parameters .. WebSphere MQ system parameters .. IMS DBCTL system parameters .. cics system parameters .. Providing a Threadsafe cics operating environment.

6 cics exits .. 121vi Threadsafe Considerations for Analyzing your exits .. Running the DFH0 STAT utility .. Exits that must be reviewed .. Identifying exits in the DB2, WMQ, and file control call paths .. Identifying dynamic plan exits in the DB2 call path .. Contacting the owner of vendor product exits .. Making your exits Threadsafe .. Removing nonthreadsafe commands .. Serializing shared resources .. Changing the CONCURRENCY definition of the exit program to Threadsafe .. Nonthreadsafe data integrity example.. Nonthreadsafe code example .. Threadsafe code example.. Code changes to make RMIXIT Threadsafe .. Coordinating and driving individual application conversions .. Changing your program definitions .. Post-conversion monitoring .. Summary .. 147 Chapter 7. Threadsafe conversion Considerations .. Global user exit Considerations .. A potential pitfall .. The solution.. Migrating WebSphere MQ regions.

7 The API crossing exit (CSQCAPX) .. Threadsafe program definition Considerations .. OPENAPI programs and additional TCB switching.. Function shipped commands .. COBOL calls .. PROGA (Quasirent) calling PROGB ( Threadsafe ).. PROGA ( Threadsafe ) calling PROGB (Quasirent).. The CSACDTA field .. Ensuring cics performance and capacity .. Analyzing the current settings .. Ensuring the availability of sufficient CPU capacity for Threadsafe regions .. Analyzing the DB2 attachment facility .. Diagnosing performance problems .. Defining the problem .. Performance hierarchy .. Key performance indicators .. Performance data sources .. 189 Contents RMF Workload Activity reports .. cics PA reports .. The DFH0 STAT utility .. Review .. 202 Chapter 8. Migration scenario .. Description of the sample application .. Migration plan .. Migration part 1 .. Identifying the in-scope exits for part 1 .. Converting the in-scope exits to Threadsafe programs.

8 Addressing nonthreadsafe commands .. Confirming performance after migration to cics Transaction Server .. Migration part 2 .. Identifying programs in scope for part 2 .. Converting user exits to be Threadsafe .. Converting application programs to be Threadsafe .. Addressing nonthreadsafe commands .. Making changes to the cics Transaction Server region .. Performance measurement .. Reports .. Charts .. Conclusions.. Additional Considerations for OPENAPI programs .. 243 Chapter 9. Threadsafe enablement using cics Tools.. Four-step cics Tools process .. Identifying candidates and capturing baseline by using cics Performance Analyzer .. Analyzing program behavior by using cics IA .. Changing cics resource definitions by using cics CM .. Testing and benchmarking the results by using cics PA and cics IA .. Application case study using the cics Tools process .. Identifying candidates and capturing a baseline.

9 Collecting SMF data for the applications.. Running the cics PA reports .. Output from the cics PA reports .. Loading the data into a historical database and DB2 .. Analyzing the program behavior .. Collecting interdependency data .. Loading cics IA dependency data .. 272viii Threadsafe Considerations for Analyzing interdependency data .. Analyzing the MAIL transaction.. Running the cics IA Command Flow feature .. Analyzing the cics IA command flow data .. The Dynamic Threadsafe Analysis report .. Analyzing the TXM* transaction .. Changing the program definitions .. Viewing the program definition .. Changing the program definition .. Viewing Audit history .. Comparing the resource definitions .. Installing the program definition .. Testing and benchmarking the results .. Running the PA Transaction Profiling report .. Rerunning the PA Threadsafe reports .. Analyzing the PA reports.. 309 Part 3. Performance and general questions.

10 313 Chapter 10. Performance case studies.. cics DB2 and file control application .. Environment .. Results .. cics WMQ and file control application .. Environment .. Results .. 323 Chapter 11. Common Threadsafe questions.. cics exits .. Defining applications as Threadsafe .. Fields and parameters.. Load module scanner .. Nonthreadsafe cics commands.. Performance .. TCB switching .. Threadsafe file control .. Using L8 or L9 TCBs .. 333 Part 4. Appendixes and related publications.. 335 Appendix A. Overview of cics Tools .. 337 cics Performance Analyzer for z/OS .. 338 Overview of cics PA .. 338 Benefits of cics PA .. 338 Contents ixComponents for cics PA .. 339 cics PA plug-in for cics Explorer .. 341 New in cics PA .. 342 cics Interdependency Analyzer for z/OS .. 343 Overview of cics IA .. 343 Benefits of cics IA .. 344 Components for cics IA.. 346 cics IA Explorer plug-in .. 350 New in cics IA .. 351 cics Configuration Manager.