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

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3.5.1 Performance SORTDEVT SYSDA INDEX(SYSIBM.DSNDSX01, SYSIBM.SQLDTX01, SYSIBM.DSNDTX01, SYSIBM.DSNDTX03, SYSIBM.DSNDTX02 KEYCARD, HAA.TABLEIX) SHRLEVEL CHANGE REPORT YES Note that the RUNSTATS suggested by the Statistics Advisor specifies the new COLGROUP option introduced in V8 to collect frequency in a column group. For the table SYSIBM.SYSTABLESPACE the statistic is for the column NAME used as a predicate in the correlated subquery to have a better filter factor estimate. The statistic for indexes specifies one index for SYSTABLESPACE and five indexes for SYSTABLES. You may consider executing RUNSTATS to collect these statistics. In DB2 V8, RUNSTATS can collect the most and least frequently occurring frequencies on almost any column or column group. RUNSTATS can also collect multi-column cardinality on almost any column group. See also 6.4, “RUNSTATS enhancements” on page 272. In many queries there are predicates on some matching and some screening columns. You can collect statistics to better reflect the total index filtering. When you have correlations and skews on some indexed and some non-indexed columns, you can collect statistics so the optimizer can more accurately estimate the number of rows which qualify from the table. The statistics that can be collected are: ► Frequency distributions for (non-indexed) columns or groups of columns ► Cardinality values for groups of non-indexed or non-leading index columns ► LEAST frequently occurring values, along with MOST for both indexed and non-indexed column distributions The new keywords: COLGROUP, MOST, LEAST, BOTH, SORTNUM, and SORTDEVT Better filter factor estimation in V8 DB2 V8 can estimate a better filter factor by using statistics inference derivation. This can result in with or without the additional statistics mentioned earlier: ► Improved query selectivity estimation using statistical inference on available statistics, when applicable ► Queries which contain two or more predicates referencing a table may get better access paths ► Significant performance improvement for some complex queries ► Consider rebinding this type of query The performance measurements show the benefits with statistics on multiple columns. Better filter factor estimation Statistics on predicate columns allow the DB2 optimizer to select a better access path as reported in the example in Figure 3-30. 74 DB2 UDB for z/OS Version 8 Performance Topics
Better filter factor estimation V7 PLAN_TABLE IXNAME METHOD MATCHCOL TSS on PLO CLAIX CLBIX BLAIX 0 1 4 4 Figure 3-30 Better filter factor estimation 0 2 1 1 V8 PLAN_TABLE IXNAME METHOD MATCHCOL TSS on PLO BLAIX CLBIX CLAIX 0 1 1 1 0 1 This figure shows a join of four tables and two join predicates between tables PLO and CLA. The plan table for V7 shows a join of table PLO and CLA using NLJ that is followed by a join to table CLB and BLA using hybrid join. In DB2 V8, the same queries allow the DB2 optimizer to find a better access path applying earlier a better filtering factor. The sequence of join of four tables changes: table BLA, that was processed last, becomes the second table scanned using NLJ, as the tables that follow. In DB2 V8, the hybrid join method is not used. The measurements of this example show: ► Elapsed time = 56.4 seconds in V7 to 19.1 seconds in V8 (66% reduction, a factor of 3) ► CPU time = 39.1 seconds in V7 to 12.4 seconds in V8 (68% reduction, a factor of 3.2) The improvement ratio can be even more significant in complex queries involving more tables and more predicates. Access path improvements - multi-column statistics Measurements on other queries from the sample workload show improvements in CPU time resulting from a better access path as shown in Figure 3-31. 60 50 40 30 20 10 V7 DEGREE(1) V8 DEGREE(1) 3X 1 0 2 Elapsed sec CPU sec 3.2X Chapter 3. SQL performance 75
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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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Page 58 and 59: Macro Parameter Old value New value
Page 60 and 61: 28 DB2 UDB for z/OS Version 8 Perfo
Page 62 and 63: ► Parallel sort enhancement Paral
Page 64 and 65: Characteristics of the host variabl
Page 66 and 67: 3.1.4 Performance Update 10 rows us
Page 68 and 69: ► Complexity of the fetch. The fi
Page 70 and 71: ► More rows per one SQL statement
Page 72 and 73: 3.2.1 Creating MQTs MQTs compared t
Page 74 and 75: Special register CURRENT REFRESH AG
Page 76 and 77: the materialized query table. If it
Page 78 and 79: Figure 3-9 MQTs and short running q
Page 80 and 81: ► The elapsed time is 22 times sm
Page 82 and 83: Figure 3-13 Regrouping on MQT resul
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Page 86 and 87: Star Schema Figure 3-15 Star schema
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Page 92 and 93: 3.3.4 Performance Sparse index for
Page 94 and 95: V8 Star Join Access Path Figure 3-2
Page 96 and 97: 3.3.5 Conclusion Star join workload
Page 98 and 99: . SELECT * FROM PAOLO.TORDER WHERE
Page 100 and 101: But not all mismatched numeric type
Page 102 and 103: V8 shows that PL is joined with CV
Page 104 and 105: Query performance problem Lack of m
Page 108 and 109: 3.5.2 Conclusions Figure 3-31 Acces
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Page 120 and 121: 100 Inserts activated trigger 100 t
Page 122 and 123: 3.10.2 Conclusion 100 Inserts activ
Page 124 and 125: stores the selected columns from ea
Page 126 and 127: While there is no optimistic lockin
Page 128 and 129: FETCH FROM Figure 3-45 FETCH syntax
Page 130 and 131: ► Measurement data collected with
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Page 138 and 139: 3.12.5 Conclusion Multi-row FETCH a
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Page 142 and 143: 3.14.2 Conclusion Percent reduction
Page 144 and 145: 3.15.1 Installation commands. Of co
Page 146 and 147: Figure 3-47 Explain of the old cons
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Page 150 and 151: Figure 3-50 Suggested RUNSTATS stat
Page 152 and 153: Looking at the explanation, we can
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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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--------------------------- -------
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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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Figure 5-4 BACKUP SYSTEM FULL measu
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5.1.2 Conclusion The BACKUP SYSTEM
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Figure 5-7 shows the sliding scale
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Maybe you have implemented a space
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For dynamically prepared queries, D
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► CHAR(8) to VARCHAR(8) ► CHAR(
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Before ALTER INDEX add column, a ta
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30 25 20 15 10 Figure 5-12 FETCH CP
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Percent of index pages Avg. Index L
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300 250 200 time in seconds 150 100
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REORG REBALANCE We executed and mea
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5.4 Volatile table 5.4.1 Conclusion
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If explicit clustering for a table
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Load table of 20M rows, 10 partitio
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Times in seconds 20 18 16 14 12 10
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RUNSTATS INDEX PARTITION of a DPSI
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Note that when the qualified partit
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► “NO” - Values in such colum
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5.6.10 Support for more than 245 se
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6.1 Online CHECK INDEX Online CHECK
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SORTOUT DD UNIT=SYSDA,SPACE=(CYL,(5
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- SORT 6 indexes in parallel - CHEC
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make DB2 take the maximum paralleli
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6.3 LOAD and UNLOAD delimited input
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6.3.2 Conclusion We measured the CP
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Options for cardinality and distrib
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► Number of column groups: 1 ►
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cases is the total time of RUNSTATS
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6.4.5 Conclusion Statistics Advisor
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goals for end-user services. We sho
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alanced across all members. With th
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method. Prior to DB2 V8 those array
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when compared to DB2 V7. At the ser
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7.2.2 Performance - Distributed cli
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Recommendation If you currently do
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► The DB2 Universal JDBC type 4 D
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WebSphere z/OS - DB2 z/OS V8 - Serv
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DB2 Universal Type 4 Driver - JDBC
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Use DB2 Connect when a high amount
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JCC Type 4 Direct 4:3 Concentration
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The SYSIBM.INDOUBT table and the pa
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Batch updates A batched update is a
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Example In DB2 V8 SQL/XML publishin
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INSERT INTO PUB_TAB(DOC) SELECT XML
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7.5.3 Conclusion The new XML publis
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A second role of the managed server
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7.6.3 Performance The following inf
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Impact on coupling facility: You do
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Table 8-1 shows extracts from DB2 P
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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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