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

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6.3.2 Conclusion We measured the CPU time for both LOAD and UNLOAD using three variations (internal format, external format, and delimited format) and our tested hardware was a z900 Turbo. There are 10 columns, including 4 CHAR, 1 VARCHAR, 3 DECIMAL, 1 SMALLINT and 1 DATE and no index exists in our test table. Delimited requires using external format for numeric. For example, INTEGER or SMALLINT is treated as if they were INTEGER EXTERNAL, and DECIMAL is treated as DECIMAL EXTERNAL. DATE is always treated as EXTERNAL, which causes the DATE fields to always have a large impact on UNLOAD performance, even though you might prefer internal format in several cases like migrating the DATE data to a different table. The results are shown in Table 6-1. Table 6-1 Delimited Load and Unload CPU comparisons External is more expensive than internal because DECIMAL and SMALLINT data in external format has to contain a character string that represents a number in specific forms. However, it should be noted that external performs significantly worse than internal, especially with UNLOAD. When compared to LOAD and UNLOAD of external undelimited format, delimited format LOAD and UNLOAD have more impact on performance. It makes sense because in UNLOAD delimited format DB2 has to build the output data to be either in character string or numeric external format, and also has to add column delimiters (default is comma) and a double quotation mark (") for the character string and a period (.) for the decimal point character. LOAD costs more because of the need to scan the VARCHAR data to define the length. In our test UNLOAD of external format significantly increased CPU time compared to internal format. 6.4 RUNSTATS enhancements In this section we first show some performance improvements in executing RUNSTATS with different options, and then we discuss the new function which allows us to gather distribution statistics. 6.4.1 General performance improvements Table 6-2 shows the measurements for RUNSTATS of a table with 10 million rows and 6 indexes. The measurements were implemented on a IBM z900 Series 2064 processor. Table 6-2 Summary of RUNSTATS improvements RUNSTATS DB2 V7 (sec.) DB2 V8 (sec.) Delta CPU Delta ET option CPU Elapsed CPU Elapsed % % 272 DB2 UDB for z/OS Version 8 Performance Topics internal external delimited delta (del/ext) LOAD (sec.) 11.41 16.3 26.5 +63% UNLOAD (sec.) 13.3 30.57 34.75 +14% TABLESPACE 15.7 39 8.6 40 -45.23 2.57
RUNSTATS option TABLE 137 140 115 118 -16.06 -15.72 TABLE and 6 INDEXES 6.4.2 DSTATS DB2 V7 (sec.) DB2 V8 (sec.) Delta CPU Delta ET CPU Elapsed CPU Elapsed % % 189 193 168 173 -11.12 -10.37 The RUNSTATS utility has been enhanced in V8 and can collect distribution statistics on any column or groups of columns, indexed or non-indexed columns, specified by table level. This enhancement lets the DB2 optimizer calculate more accurately the filter factor of a query and helps to improve SQL performance. For versions prior to V8 you can use a tool called DSTATS (Distribution Statistics for DB2 for OS/390) which you can download from the Web site: http://www.ibm.com/support/docview.wss?uid=swg24001598 This tool is available for use with DB2 V5, V6, and V7. DSTATS is a standalone DB2 application program, written in PL/I, which contains dynamic and static SQL statements. The tool collects additional statistics on column distributions and column frequencies that were not collected by RUNSTATS before DB2 V8. With DB2 V8, equivalent function is provided by the RUNSTATS utility. The enhanced RUNSTATS utility collects additional information on column distribution and frequencies, and updates the DB2 catalog with the more accurate statistics. It greatly enhances the performance of the query if there are non-uniform data distributions in your tables or indexes. 6.4.3 Description of distribution statistics in V8 When there is a skewed distribution of values for a certain column, this can cause bad response time of a query, especially in ad hoc query applications. The collection of correlation and skew statistics for non-leading indexed columns and non-indexed columns can help the optimizer to compute accurate filter factors. This leads to better access path selection and improves query performance. The enhancement of the RUNSTATS utility allows you to use RUNSTATS to collect distribution statistics on any column in your tables, whether or not the columns are part of an index, and whether or not the columns are the leading columns of an index. It updates the DB2 catalog with the specified number of highest frequencies and optionally with the specified number of lowest frequencies. The new functionality also optionally collects multi-column cardinality for non-indexed column groups and updates the catalog. The summary of the new functionality of RUNSTATS is as follows: ► Collect distribution statistics on any column, or groups of columns, indexed or non-indexed, specified at the table level ► Frequency distributions for non-indexed columns or groups of columns ► Cardinality values for groups of non-indexed columns ► LEAST frequently occurring values, along with MOST frequently occurring values, for both index and non-indexed column distributions (DB2 V7 only gathers the most frequently occurring value) Chapter 6. Utilities 273
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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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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
Page 284 and 285: Times in seconds 20 18 16 14 12 10
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
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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 306 and 307: Options for cardinality and distrib
Page 308 and 309: ► Number of column groups: 1 ►
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 322 and 323: 7.2.2 Performance - Distributed cli
Page 324 and 325: Recommendation If you currently do
Page 326 and 327: ► The DB2 Universal JDBC type 4 D
Page 328 and 329: WebSphere z/OS - DB2 z/OS V8 - Serv
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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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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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