IMS Performance Hints and Tips - IMS UG August 2012 Sao Paulo

1 © 2012 IBM Corporation

August 2012 IMS User Group, Sao Paulo, Brazil

IMS Performance Hints and Tips

Mike GonzalesIBM Software Group


2012 IMS Technical Conference , Australia

222

© Copyright IBM Corporation 2012. All rights reserved.U.S. Government Users Restricted Rights - Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp.

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Part 1 : The Mechanic’s Tool Kit



Log Analysis Tool(s)

• Standard Utilities

– DFSERA10

– DFSILTA0

– DBFILTA0

– DFSISTS0

• KBLA (pre IMS V12)

• IMS Performance Analyzer

• IMS Problem Investigator

• IBM Transaction Analysis Workbench

• Set TRANSTAT=Y

– (DFSDFxxx, TRANSACT macro, CREATE/UPD TRAN/PGM)

– Enhanced transaction statistics



Sampling Tool

• IBM Application Performance Analyzer

• Macro 4 Freeze Frame

• Compuware STROBE

• IBM MVS Hardware Instrumentation Service (HIS)



System Resource Reporting

• IBM Resource Measurement Facility (or equivalent)

• Tivoli Decision Support (TDS) for IMS



Part 2 : Infrastructure – The Chasis



MVS Workload Manager (WLM)

• Limit service periods to 30 or fewer

• Use all 6 Importance values (1 to 5, + Discretionary)

• Limit use of CPU Critical

• Define IMS transaction response time goals for IMS TM

• Use common service classes for multiple subsystems

• Use report classes for granular feedback/charge back

• Target Performance Index 0.8 – 1.1 during peaks

• Service Coefficients : CPU 1.0 SRB 1.0 MSO 0.5 IOC 0.0



Global Resource Serialization (GRS)

• Convert RECON RESERVEs to ENQs in GRS STAR

• Exclude RECONs for access outside of a parallel sysplex



Resource Access Control Facility (RACF)

• Cache, cache, cache

– VLF

– CF

– IMS OTMA

– IMS Connect



Part 3 : IMS – The Engine



IMS Scheduling – Program Load

• Program Preload

– APA – Load Module Summary

– STROBE – SVC122 count

– PRLD=suffix of DFSMPLxx

• Library Routine Retention (LRR) – DFSINTxx+CEELRRIN or CEELRRXP

• Add IMS program libraries to VLF (stores load modules in data spaces)

• LLA – FREEZE (manages TTR/directory information, FREEZE ensures they

remain in virtual storage)

• STEPLIB the application

program libraries

that are in LINKLIST



IMS Scheduling – Scheduling Blocks/Pools

• Resident PSB/DMB – loaded during IMS initialization

• Size pools to avoid cast outs

• PWFI – reuse scheduled resources, maximize local-first

scheduling in shared queues

• IFPs – Schedule once per region execution

• BMPs – WFI and looping/waiting schedule once

• PST=xxx

– Set high enough to prevent excessive GETs/FREEs



IMS Scheduling – Shared Queues False Scheduling

• CFCC 16 reduces global false scheduling with multiple

members in a shared queues group

• IMS V11 reduces local false scheduling between parallel regions



IMS Page Fixing

• DFSFIXnn

– FP, DMBD, PSBD, DLDP, DLMP, DPSB, QBUF

– V12 backs 31-virt with 64-real for DBWP, DLDP, DLMP, DPSB, and PSBW

• DB Buffers – specify fix options in DFSVSMxx

• Watch out for SORT !!!

– Consider WLM Storage Critical for DB2 DBM1

• EXVR=1

– Page fix Queue Buffers

• EXCPVR=1

– Page fix OSAM buffer pool



IMS Database Locking

• Use Program Isolation as long as possible

• With IRLM :

– use SCOPE=NODISCON

� Prevent batch connect/disconnect when IMS control region is down

– Use DEADLOK > 5

� Use millisecond based detection cycles

• Use LOCKTIME (DFSVSMxx/DFSVSAMP)

� Sets timeout for waiting on lock request

� Return ‘BD’ or U3310

• Use minimum PROCOPT needed



IMS Database Access Methods

• Performance by design

– DEDB

– HDAM/PHDAM – OSAM

– HDAM/PHDAM - VSAM

– HIDAM/PHIDAM – OSAM

– HIDAM/PHIDAM – VSAM

• DEDB + Secondary Index

– HDAM/PHDAM + Secondary Index



IMS Database Buffers

• Adjust to workload, alter dynamically (IMS V12)

• Page fix if not storage constrained

• IMS Buffer Pool Analyzer

– Use buffer life as tuning metric



IMS Logging

• IMS V12 OLDS/SLDS Striping

• Adjust log buffers to avoid buffer waits

• Use 64-bit buffer pool (OLDS BLKSIZE = 4K * n)

• WADS mirroring max 20 Km



IMS Logging - 64-bit Log Buffers / 1M pages

• IEASYSxx

– LFAREA=nn (%, G, or M)

• OLDS allocated by DFSMS

– Extended format (striped)

• DFSVSMxx

– BUFSTOR=64

– BLKSZ=(4K * n)



IMS Queue Buffers

• Adjust number to prevent QBUF waits

• Size according to majority of queue activity



IMS Connect

• Persistent socket

– Connect once then multiple write/read iterations for multiple transactions before Close (Disconnect)

– This will keep the socket open – make sure you have defined enough sockets

• Send ICON messages as a single message with all

components

• Ensure TCPIP NODELAYACK is specified on TCP/IP

PORT or GATEWAY statements



zIIP/zAAP support

• Request response processing for authorized CQS clients is

eligible to run on a zIIP

• Examples

• When the IMS control region is running with IMS Shared

Message Queues or Shared IMS Fast Path Message Queues

enabled

• When the IMS Resource Manager address space is using a

resource structure

• IMS Java runs on zAAPs



Part 4 : Outside the Box – The Accessories



WMQ

• Tune MQ buffers and pagesets

• Review and disable internal traces

• Consider MQGET(WAIT) loop if IMS Msg Queues not needed

• Preload WMQ routines in MPRs

– CSQQDEFV, CSQQCONN, CSQQDISC, CSQQTERM, CSQQINIT, CSQQBACK, CSQQCMMT, CSQQESMT, CSQQPREP, CSQQTTHD, CSQQWAIT, CSQQNORM, CSQQSSOF, CSQQSSON, CSQFSTAB,CSQQRESV, CSQQSNOP, CSQQCMND, CSQQCVER, CSQQTMID, CSQQTRGI, CSQFSALM, CSQAPRH



DB2

• DB2 thread counts – make sure enough storage for DB2

• Reduce/prevent global contention



RRS

• Avoid RRS

• Monitor and resize DELAYED UR logstream to avoid

offloads

• IMS V12 XCFIMS for Commit Mode 1 instead of RRS



CICS - DBCTL

• IMS V12 DRA Open Thread TCB – CICS Threadsafe



Contact Information

For assistance or service engagement requests contact:

Jeff Hook, Manager IMS Technical Services

[email protected]

Mike Gonzales, IMS Technical Specialist

[email protected]

Technology

IMS Performance Hints and Tips - IMS UG August 2012 Sao Paulo