© Copyright IBM Corporation 2009
IBM Software Group
IMS Buffer Pool Tuning
Manoj Kaveri
Cert IMS DBA
Large Healthcare Payo...
IMS Storage
 VSAM Control Interval : VSAM works with a logical data area known as a
control interval (CI). The default CI...
IMS Database Types
 Full- Function Database
HSAM,HISAM,HDAM,HIDAM
 Fast-Path Database
DEDB,MSDB
 HALDB Database
PHDAM,P...
4
Introduction
 Buffer poolBuffer pool are areas of virtual storage that temporarily stores data
during run-time.
 Alloc...
5
Buffer Pool Objective
Eliminating I/O reduces
CPU costs
Increase Number of
Page Hit Ratio.
Reduce CPU Time
Reduce Number...
6
Buffer Pool Component Located
DLI NOT WAIT
IMS
Controller
IMS DB
IMS
PC
PROGRAM ELAPSE TIME
IMS Buffer Space
IMS DB
IMS ...
7
How to meet the performance Objective ?
Business Scenario :

Buffer spool option be selected only if the user has estab...
8
How to meet the performance Objective ?
Problem Statement :
 Buffer pool was not defined according to the VSAM CI or OS...
9
How to meet the performance Objective ?
Solution:
 IMS may build multiple VSAM pools. Each pool may have multiple sub p...
10
How to meet the performance Objective ?
Change Desc:Change Desc:
 VSAM ESDS Buffer poolVSAM ESDS Buffer pool
POOLID=SP...
11
Test Results..
 B&UT Testing : IBM GR Team – Test Results
Description Base Converted
Run1
CPU UNITS 3,026,234 2,843,99...
12
Test Results..
 SIT Testing : Client Technical Expert Group – Test Results
Description Base Converted
Run1
Converted R...
13
Business Benefits…
 Buffer pool concept will be applicable to batch & online application.
 By proposing IMS buffer-po...
14
Performance Dependent Parameters…
 Performance of XNC100JD dependent on the below parameters
 Region Parameters:
• Wh...
15
Implementation Method…
 Batch Jobs
- Update the DFSVSAMP DD Control Cards
 Online Program
- DFSVSMxx member in IMS.PR...
16
For more information
 IMS Full Function Database Use of VSAM Buffer Pools
-http://www-03.ibm.com/support/techdocs/atsm...
17
IMS Buffer Pool is …
… Just
Great !
THANK YOU …..ANY QUESTIONS
AMS Share-Net | Oct 2010
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IMSBufferpool Tuning concept AMS presentation v01

  1. 1. © Copyright IBM Corporation 2009 IBM Software Group IMS Buffer Pool Tuning Manoj Kaveri Cert IMS DBA Large Healthcare Payor Account in US Oct 2010
  2. 2. IMS Storage  VSAM Control Interval : VSAM works with a logical data area known as a control interval (CI). The default CI size is 4K bytes, but it can be up to 32K bytes. The CI contains data records, unused space, and a CI descriptor field.  Most commonly used VSAM file in IMS. - Key Sequence Data Set (KSDS) Contain two components: INDEX and DATA -Entry Sequence Data Set (ESDS) Contain single component: DATA.  OSAM Block Size : OSAM works with a logical data area know as a block size.  VSAM dataset can store data up to 4GB & OSAM up to 8GB  Identify the file type in DBD DBD NAME=XXLA01DB, ACCESS=(HIDAM,VSAM) or ACCESS=(HIDAM,OSAM) AMS Share-Net | Oct 2010 Innovative Improved Usability Open Standards
  3. 3. IMS Database Types  Full- Function Database HSAM,HISAM,HDAM,HIDAM  Fast-Path Database DEDB,MSDB  HALDB Database PHDAM,PHIDAM,PSINDEX  Identify the database type based on access methods in DBD DBD NAME=XXLA01DB, ACCESS=(HIDAM,VSAM) Innovative Improved Usability Open Standards
  4. 4. 4 Introduction  Buffer poolBuffer pool are areas of virtual storage that temporarily stores data during run-time.  Allocate sufficient buffers in the IMS database buffer pools to prevent I/O that results from an application program having to reread data previously brought into the pool.  Careful choice of sub pool sizes and matching against database block sizes and frequency of database references is required.  Type of buffer pools – Based on file type 1. VSAM Buffer Pool - Define VSAM sub pools using the VSRBF control statement 2. OSAM Buffer Pool - Define OSAM subpools are defined using the IOBF.  Buffer Sizes can be 5 KB, 1 KB, 2 KB, 4 KB, 8 KB and multiple of 4KB.  Buffer Size should be selected based on CI SIZE of VSAM or BLOCK SIZE of OSAM file. Innovative Improved Usability Open Standards AMS Share-Net | Oct 2010
  5. 5. 5 Buffer Pool Objective Eliminating I/O reduces CPU costs Increase Number of Page Hit Ratio. Reduce CPU Time Reduce Number of Page SWAP. I/O Avoidance -Keep data in memory -Buffer Pool. Optimize memory Usage Batch Jobs -Achieve your batch requirements - Maximize throughput Transactions -Improve productivity -Improve clients satisfaction Reduce Elapse Time AMS Share-Net | Oct 2010
  6. 6. 6 Buffer Pool Component Located DLI NOT WAIT IMS Controller IMS DB IMS PC PROGRAM ELAPSE TIME IMS Buffer Space IMS DB IMS Program DLI ELAPSE TIME APPLICATION DLI IWAIT DB Access AMS Share-Net | Oct 2010
  7. 7. 7 How to meet the performance Objective ? Business Scenario :  Buffer spool option be selected only if the user has established performance objectives and know how the current system is performing.  Understand Current Business Scenario : • Batch job/Online Program is access Large number of IMS Database. • Database type and Access methods. -Database type : Full-Function, Fast-Path, HALDB -Access Method : HISAM,HDAM,HIDAM,PHDAM,PHIDAM • IMS Storage and Control Interval Verification. - Verify CI Size of VSAM INDEX & DATA Component. - Verify Block Size of OSAM file. AMS Share-Net | Oct 2010
  8. 8. 8 How to meet the performance Objective ? Problem Statement :  Buffer pool was not defined according to the VSAM CI or OSAM Block size.  Buffer pool was not been divide into sub-pool for Data (D –VSAM Data component, ESDS) and Index (I- VSAM Index Component).  Common buffer control card has been used across all the batch jobs.  Existing production code : DFSVSAMP DD DSN=TEST.PROCLIB (XXVSAMP) 18432,4 16384,4 12288,200 8192,700 IOBF=(2048,4,N,N) IOBF=(4096,500,N,N) IOBF=(6144,300,N,N) AMS Share-Net | Oct 2010
  9. 9. 9 How to meet the performance Objective ? Solution:  IMS may build multiple VSAM pools. Each pool may have multiple sub pools.  A VSAM pool is defined by a POOLID= statement in the DFSVSMxx member for online systems or the DFSVSAMP data set for batch and utility jobs.  Suggest Changes : POOLID=SP01 VSRBF=8192, 700, D DBD= XTDBD01 (1, SP01) POOLID=SP02 VSRBF=12288, 200, D VSRBF=10240, 500, I DBD= XTDBD02 (1, SP02) IOBF=(2048,4,Y,Y) OPTIONS, VSAMFIX= (BFR, IOB), BGWRT= (YES, 50) By dividing buffer pools in data and index component number of page hit ratio can be increased and reduce the I/O transfer rate/sec, which results in reduction of elapse time, CPU units, I/O transfer counts.  Buffer pool has been defined according to the VSAM CI or OSAM Block Size. AMS Share-Net | Oct 2010
  10. 10. 10 How to meet the performance Objective ? Change Desc:Change Desc:  VSAM ESDS Buffer poolVSAM ESDS Buffer pool POOLID=SP01 /* POOLID: Define buffer pool name, SPO1: is buffer pool name. Its user define namePOOLID=SP01 /* POOLID: Define buffer pool name, SPO1: is buffer pool name. Its user define name VSRBF=8192, 700, D /*-VSRBF: Sub pools in the pool are defined by the VSRBF= statements which followVSRBF=8192, 700, D /*-VSRBF: Sub pools in the pool are defined by the VSRBF= statements which follow /*the POOLID= statement - 8192-: Buffer Size -Sub pool has a buffer size of 8192,/*the POOLID= statement - 8192-: Buffer Size -Sub pool has a buffer size of 8192, /*700 : Number of buffer pool/No. of block in SPO1 buffer pool./*700 : Number of buffer pool/No. of block in SPO1 buffer pool. D : Data component will use this buffer pool SP01.D : Data component will use this buffer pool SP01.  VSAM KSDS Buffer poolVSAM KSDS Buffer pool POOLID=SP02POOLID=SP02 VSRBF=12288,200,D / * D : Indicates that data component can use this subpoolVSRBF=12288,200,D / * D : Indicates that data component can use this subpool VSRBF=10240,500,I /* I : Indicated the only index component can use this subpool.VSRBF=10240,500,I /* I : Indicated the only index component can use this subpool. DBD=XTDBD02 (1,SP02) /* XTDBD02 : DBD name corresponding to dataset.DBD=XTDBD02 (1,SP02) /* XTDBD02 : DBD name corresponding to dataset. Job1 Shared Buffer Pools Job2 Online Scr Remember:Remember: Performance dependencePerformance dependence on whether shared bufferon whether shared buffer used by multiple programused by multiple program during run-timeduring run-time AMS Share-Net | Oct 2010
  11. 11. 11 Test Results..  B&UT Testing : IBM GR Team – Test Results Description Base Converted Run1 CPU UNITS 3,026,234 2,843,993 CPU Time 00:01:14.88 00:01:02.37 SERV UNITS 3,092,247 2,906,908 SRB UNITS 51,595 48,524 I/O UNITS 14,418 14,391 Execution Time (step XNC100X) 00:10:55.09 00:05:30.62 DLI Statistics Report Calls Base Convert GU 47 41 GN 83,342 83,343 GNP 2,062,941 2,062,981 GHU 6 6 DB (TOTAL) 2,146,342 2,146,383 CHKP 42 42 LOG 294 294 Remember 1:Remember 1: Performance should bePerformance should be compared based on No. ofcompared based on No. of DLI calls issued & No. ofDLI calls issued & No. of record accessed inrecord accessed in program.program. AMS Share-Net | Oct 2010
  12. 12. 12 Test Results..  SIT Testing : Client Technical Expert Group – Test Results Description Base Converted Run1 Converted Run2 Converted Run3 CPU UNITS 10,264,284 9,914,169 9,538,354 9,031,724 CPU Time 00:04:06.28 00:04:05.32 00:03:56.02 00:03:36.71 SERV UNITS 10,584,075 10,227,066 9,842,507 9,325,137 SRB UNITS 233,312 230,039 226,202 217,536 I/O UNITS 86,479 82,858 77,951 75,877 Execution Time (step XNC100X) 00:30:06.43 00:24:18.70 00:20:10.64 00:12:16.73 Remember 2:Remember 2: Whether the IMS1/IMS2Whether the IMS1/IMS2 region database has beenregion database has been re-org recentlyre-org recently AMS Share-Net | Oct 2010
  13. 13. 13 Business Benefits…  Buffer pool concept will be applicable to batch & online application.  By proposing IMS buffer-pool concept we are able to reduce 10-20% of elapse time, CPU units, I/O transfer counts.  Implementing buffer-pool concept into there respective account will add values to clients and will be able to meet SLA, as it will reduce application elapse time.  Dividing buffer pools in data and index component number of page hit ratio can be increased and reduce the I/O transfer rate/sec  Supports additional new opts Included – BGWRT (Back Ground Write) % used for parallel write operation to database and buffer pool can be released during database processing. IMS BufferIMS IMS AMS Share-Net | Oct 2010
  14. 14. 14 Performance Dependent Parameters…  Performance of XNC100JD dependent on the below parameters  Region Parameters: • Whether these database are used by other program during the batch job execution. • Shared buffer used by other program for loading the data. • Whether the IMS1/IMS2 region database has been reorganized recently.  Application Parameters: • No. of record retrieved from the database.. • No. of DLI call issued by the program. • BGWRT- The best percentage value to be specified will change depending on whether the program is re- accessing the buffers or not. • Background Write: In general, maximum benefit occurs in sequential update processing. AMS Share-Net | Oct 2010
  15. 15. 15 Implementation Method…  Batch Jobs - Update the DFSVSAMP DD Control Cards  Online Program - DFSVSMxx member in IMS.PROCLIB for online systems Example 1: POOLID=VSM1 VSRBF=4096,3000,D VSRBF=12288,2000,I VSRBF=32768,12,D Since the second VSRBF statement builds an index subpool, the first and third subpools may only be used for data components. The second subpool may only be used for index components. Assumption:Assumption: Application is IMS BatchApplication is IMS Batch or Online Programor Online Program AMS Share-Net | Oct 2010
  16. 16. 16 For more information  IMS Full Function Database Use of VSAM Buffer Pools -http://www-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/FLASH10240  IMS Buffer Pool Analyzer - http://publib.boulder.ibm.com/infocenter/dzichelp/v2r2/index.jsp? topic=/com.ibm.imstools.bpl.doc.ug/bplucon_hilites.htm  IMS Performance Monitoring and Tuning Update -ibm.com/redbooks AMS Share-Net | Oct 2010
  17. 17. 17 IMS Buffer Pool is … … Just Great ! THANK YOU …..ANY QUESTIONS AMS Share-Net | Oct 2010

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