DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

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Options for cardinality and distribution statistics To support these new functionalities, several new options are introduced in the RUNSTATS utility. New keywords COLGROUP, LEAST, MOST and BOTH enable the collection of distribution statistics on any table column and group of columns. The existing keywords FREQVAL and COUNT also can be used. You can specify the following options for collecting cardinality and distribution statistics: ► COLGROUP: When you specify the COLGROUP keyword, the specified set of columns is treated as a group and RUNSTATS collects correlation statistics for the specified column group. You can specify the COLGROUP keyword repeatedly, if you want to collect statistics on a different set of columns. ► FREQVAL: This keyword controls the collection of frequent value statistics. These are collected either on the column group or on individual columns depending on whether COLGROUP is specified or not. You can specify the FREQVAL keyword together with the NUMCOLS keyword when you run RUNSTATS INDEX. But when you run table-level statistics, FREQVAL can only be specified together with the COLGROUP keyword. If FREQVAL is specified, then it must be followed by the keyword COUNT. ► COUNT: This indicates the number of frequent values to be collected. Specifying an integer value of 20 means to collect 20 frequent values for the specified columns. No default value is assumed for COUNT. This can be optionally followed by the keyword MOST (which is the default), LEAST, or BOTH. Note: The following statement: RUNSTATS TABLESPACE DBGBTEST.TSGBRUNS TABLE(ALL) INDEX(ALL) KEYCARD does collect FREQVAL values on the indexes by default. If you do not want to collect any FREQVAL data, you need to specify the following options: RUNSTATS TABLESPACE DBGBTEST.TSGBRUNS TABLE(ALL) INDEX(ALL) KEYCARD FREQVAL NUMCOLS 1 COUNT 0 ► MOST: The most frequent values are collected when the keyword MOST is specified. ► LEAST: The least frequent values are collected when the keyword LEAST is specified. ► BOTH: The most frequent values and the least frequent values are collected when the keyword BOTH is specified. Options for using sort work data sets When you are collecting distribution statistics for column groups or collecting statistics on a data-partitioned secondary index, for example, it is necessary for DB2 to use sort work to sort the statistics. As a new option of V8, you can specify the SORTDEVT and SORTNUM keywords for using dynamic allocation of the sort work data sets: ► SORTDEVT: This specifies the device type that DFSORT uses to dynamically allocate the sort work data set. ► SORTNUM: This specifies the number of required sort work data sets that DFSORT is to allocate. If you do not use dynamic allocation for the SORT program, and if you collect the statistics for which sort data is required, you have to define data sets through JCL. You need to specify ST01WKnn and STATWK01 in DD statements depending on the statistics you collect: 274 DB2 UDB for z/OS Version 8 Performance Topics
6.4.4 Performance ► ST01WKnn: You need to specify the data set name for the temporary data sets of sort input and output when collecting statistics on at least one data-partitioned secondary index. ► STATWKnn: You need to specify the data set name for the temporary data sets of sort input and output when collecting distribution statistics for column groups. Note: To calculate the approximate size (in bytes) of the ST01WKnn data set, use the following formula: 2 × (maximum record length × numcols × (count + 2) × number of indexes) The values in the formula are as follows: ► Maximum record length: The maximum length of the SYSCOLDISTATS record on which RUNSTATS is to collect frequency statistics. You can obtain this value from the RECLENGTH column in SYSTABLES. ► Numcols: The number of key columns to concatenate when you collect frequent values from the specified index. ► Count: The number of frequent values that RUNSTATS is to collect. When you plan to use distribution statistics, make sure that the following maintenance is applied for correct functionality and good performance: ► PTF UQ88754 for APAR PQ88375 provides the right value of cardinality for partitioned table spaces. ► PTF UQ91099 for APAR PQ87509 is required for correctness of frequency values. ► PTF UQ93177 for APAR PQ90884 is required for better (200%) performance. DSTATS performance comparison of V7 and V8 with PQ90884 In this test we first run RUNSTATS in V7 followed by the standalone DSTATS tool. We measure class 1 elapsed and CPU time and get the total time of both. In the second case we measure V8 RUNSTATS with distribution statistics where we collect equivalent statistics to those taken in V7 with the DSTATS tool. Before running this case we have applied the PTF for PQ90884. We use an internal query workload and the test table contains about 931k rows. The description of the test environment is: ► DB2 V7 and V8 (non-data sharing) ► Table: 1 test table in 1 table space ► Number of pages: 77601 ► Number of rows: 931,174 ► Number of indexes: 4 (1 partitioned index, 3 non-partitioned indexes) ► Number of partitions of table space: 6 ► 2 columns are non-indexed columns (used for statistics) – Column1 cardinality=15104 – Column2 cardinality=24 To explain our test case more clearly, let us show you a part of our control statements for testing. We have done equivalent RUNSTATS in V7 and V8, and we have taken equivalent statistics in V7 with the DSTATS tool, and in V8 with RUNSTATS. We are specifying 2 columns for statistics and both are non-indexed columns. The description of the statistics is: Chapter 6. Utilities 275
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ibm.com/redbooks Front cover DB2 UD
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Note: Before using this information
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2.5.3 Increased number of deferred
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4.5.2 Conclusion . . . . . . . . .
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7.4.1 ODBC Unicode support . . . .
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x DB2 UDB for z/OS Version 8 Perfor
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3-48 Consistency query - 31 New . .
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xiv DB2 UDB for z/OS Version 8 Perf
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8-5 CF Request Batching - DB2 CPU .
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xviii DB2 UDB for z/OS Version 8 Pe
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Trademarks The following terms are
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Added information The following APA
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► Added reference to June 15, 200
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Michael Parbs is a DB2 Specialist w
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Hugh Smith Jim Teng John Tobler Yoi
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xxx DB2 UDB for z/OS Version 8 Perf
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1.1 Overview 1.1.1 Architecture IBM
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- Column data type changes can be d
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1.1.3 Data warehouse 1.1.4 Performa
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Volatile (or cluster) tables, used
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In this chapter we anticipate the a
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2.1.3 I/O time 2.1.4 Virtual storag
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► The performance benchmarks for
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application that can have great pot
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Because you can significantly incre
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The possible increase in thread foo
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2.5.9 Unicode parser Important: Con
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You can keep the DBRMs in EBCDIC fo
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Macro Parameter Old value New value
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28 DB2 UDB for z/OS Version 8 Perfo
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► Parallel sort enhancement Paral
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Characteristics of the host variabl
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3.1.4 Performance Update 10 rows us
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► Complexity of the fetch. The fi
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► More rows per one SQL statement
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3.2.1 Creating MQTs MQTs compared t
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Special register CURRENT REFRESH AG
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the materialized query table. If it
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Figure 3-9 MQTs and short running q
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► The elapsed time is 22 times sm
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Figure 3-13 Regrouping on MQT resul
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EVE.EXT = 'ADD BILL' AND EVE.TXC =
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Star Schema Figure 3-15 Star schema
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merge joins and work file usage. DB
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Star join access path without a spa
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3.3.4 Performance Sparse index for
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V8 Star Join Access Path Figure 3-2
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3.3.5 Conclusion Star join workload
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. SELECT * FROM PAOLO.TORDER WHERE
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But not all mismatched numeric type
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V8 shows that PL is joined with CV
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Query performance problem Lack of m
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3.5.1 Performance SORTDEVT SYSDA IN
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3.5.2 Conclusions Figure 3-31 Acces
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Mismatched data types SELECT COUNT(
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3.7.1 Performance In V8 the paralle
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3.7.2 Conclusions Example 3-9 Multi
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3.8.2 Performance We show three exa
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3.8.3 Conclusion The measurements s
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100 Inserts activated trigger 100 t
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3.10.2 Conclusion 100 Inserts activ
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stores the selected columns from ea
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While there is no optimistic lockin
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FETCH FROM Figure 3-45 FETCH syntax
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► Measurement data collected with
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application has decidedly higher Cl
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Static updatable cursor You can see
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Multi-row FETCH with a static curso
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3.12.5 Conclusion Multi-row FETCH a
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While, for or SELECT ... FROM ...
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3.14.2 Conclusion Percent reduction
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3.15.1 Installation commands. Of co
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Figure 3-47 Explain of the old cons
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in ms = 1 and the CPU cost is 16 se
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Figure 3-50 Suggested RUNSTATS stat
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Looking at the explanation, we can
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The Plug-In Options screen of Stati
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Before the introduction of MQTs, DB
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126 DB2 UDB for z/OS Version 8 Perf
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► Larger VSAM CI sizes: DB2 V8 in
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4.1.1 Performance support caused al
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Regression is about 5% better than
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The results indicate no significant
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Important: 4.1.2 Conclusion If you
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However, the combined impact of oth
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Frees up space below the bar for ot
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from the hiperpools, they were not
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So, we advise you to not overalloca
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See 4.3, “Monitoring DBM1 storage
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Table 4-4 System storage configurat
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Stack 11356 21033 85% 8648 19799 12
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KB 600 500 400 300 200 100 0 Figure
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For the same buffer pool size and o
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4.2.3 Conclusion Nondistributed per
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Important: With PTFs UK04394 (DB2 V
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- DATASPACE BP CONTROL BLOCKS = 0 M
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The EXTENDED REGION SIZE (MAX) is t
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RDS OP POOL (MB) N/A RID POOL (MB)
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As you can now appreciate, it is im
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Megabytes A V7 Customer DBM1 Thread
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4.5.1 Performance The most buffer p
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4.6.1 Performance maintained in a 2
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4.6.2 Conclusion We can conclude th
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service for Unicode conversions, an
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overcome this, when DB2 Connect is
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INSERT HV1 1200 HV2 1200 SELECT HV1
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AIX C-program Conversion Routines P
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4.7.1 Performance The improvements
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In October 2003, a new enhancement
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UseServerEncoding data source prope
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4.8.1 Performance 4.8.2 Conclusion
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Multilevel security with row-level
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► The security level that defines
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DB2 must call RACF for this dominan
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4.9.2 Conclusion The CPU increase c
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4.10.1 Performance VSAM does not kn
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4.10.2 Conclusion 4.10.3 Striping A
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5 4 3 2 1 0 9109TLLB 4 Parallel DB2
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This message is completed with the
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This enhancement is introduced by P
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This record is activated by: -START
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an online transaction with very sim
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5.1 System level point-in-time reco
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BACKUP SYSTEM During backup DB2 rec
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Figure 5-1 FRBACKUP PREPARE elapsed
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Page 258 and 259: 5.1.2 Conclusion The BACKUP SYSTEM
Page 260 and 261: Figure 5-7 shows the sliding scale
Page 262 and 263: Maybe you have implemented a space
Page 264 and 265: For dynamically prepared queries, D
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Page 268 and 269: Before ALTER INDEX add column, a ta
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Page 272 and 273: Percent of index pages Avg. Index L
Page 274 and 275: 300 250 200 time in seconds 150 100
Page 276 and 277: REORG REBALANCE We executed and mea
Page 278 and 279: 5.4 Volatile table 5.4.1 Conclusion
Page 280 and 281: If explicit clustering for a table
Page 282 and 283: Load table of 20M rows, 10 partitio
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Page 286 and 287: RUNSTATS INDEX PARTITION of a DPSI
Page 288 and 289: Note that when the qualified partit
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Page 292 and 293: 5.6.10 Support for more than 245 se
Page 294 and 295: 6.1 Online CHECK INDEX Online CHECK
Page 296 and 297: SORTOUT DD UNIT=SYSDA,SPACE=(CYL,(5
Page 298 and 299: - SORT 6 indexes in parallel - CHEC
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Page 302 and 303: 6.3 LOAD and UNLOAD delimited input
Page 304 and 305: 6.3.2 Conclusion We measured the CP
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Page 310 and 311: cases is the total time of RUNSTATS
Page 312 and 313: 6.4.5 Conclusion Statistics Advisor
Page 314 and 315: goals for end-user services. We sho
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Page 324 and 325: Recommendation If you currently do
Page 326 and 327: ► The DB2 Universal JDBC type 4 D
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Page 332 and 333: Use DB2 Connect when a high amount
Page 334 and 335: JCC Type 4 Direct 4:3 Concentration
Page 336 and 337: The SYSIBM.INDOUBT table and the pa
Page 338 and 339: Batch updates A batched update is a
Page 340 and 341: Example In DB2 V8 SQL/XML publishin
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Page 344 and 345: 7.5.3 Conclusion The new XML publis
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Page 352 and 353: Impact on coupling facility: You do
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and secondary GBP structures have t
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DB2 member already has the table sp
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8.2.1 Performance We ran a number o
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esolve any contention. This extra a
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There is also no need to use RELEAS
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Table 8-12 DB2 I/O CI Limit Removal
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8.5 Miscellaneous items In this sec
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DB2 V8 improves Restart Light. If i
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9.1 Unicode catalog DB2 for z/OS su
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that all applications are converted
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- CLASST: Specifies the threshold a
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From these measurements we observe
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Class 1 CPU time (MSEC) 200 150 100
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dynamic statement cache. If activat
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that everything is ready. This step
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Table Number of rows SYSDATABASE 75
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In Figure 9-7 we describe the perfo
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Old - Query 5 New - Query 5 CPU (se
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Query 35 36 Old DSNTESQ CPU 1 hr 1
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10.1 DB2 Estimator DB2 Estimator V8
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- REAL AND AUXILIARY STORAGE This i
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Another use is during back out of a
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In DB2, the IBM Data Encryption too
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The utilities ran on a G7 Turbo wit
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time Figure 10-1 DB2 HPU vs. UNLOAD
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DSNTIAUL with multi-row fetch The r
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A.1 Maintenance for DB2 V8 The APAR
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APAR # Area Text PTF and Notes PQ88
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APAR # Area Text PTF and Notes PK21
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B.1 DB2 PE Storage Statistics trace
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Storage heading Description 24 BIT
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C.1 DB2 SQL PA additional reports N
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|is the last matching predicate. Ap
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|ANL6052I *** NOTE: | |This index i
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PREDICATE ANALYSIS ----------------
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D.1 DB2 EXPLAIN EXPLAIN describes t
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Table D-2 PLAN_TABLE contents and b
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Column Type Content SORTC_ORDER BY
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Column Type Content OPTHINT CHAR(8)
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D.1.3 DSN_FUNCTION_TABLE You can us
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Example: D-1 Creating DSN_STATEMENT
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Column Type Content BIND_QUALIFIER
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ICF integrated catalog facility ICF
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► DB2 UDB for z/OS V8: Through th
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character set 174 CHECK DATA 262 CH
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Equi-join predicates 54, 402 Equiva
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MINSTOR 145-146 Mismatched data typ
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PQ84160 378, 387 PQ85764 387 PQ8584
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Sort tree nodes 144 SORTDATA 268 SO
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306 Universal Driver for SQLJ and J
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DB2 UDB for z/OS Version 8 Performa
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