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

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Table 8-12 DB2 I/O CI Limit Removal - Non-data sharing Activity With I/O CI Limit I/O CI Limit Removed List Prefetch Requests 57,889 58,165 List Prefetch Reads 317,000 56,122 List Prefetch Pages Read / List Prefetch Reads The values listed verify that the limit on CIs per DB2 I/O has been removed. The number of List Prefetch Reads has reduced dramatically, with a corresponding increase in the number of pages read per List Prefetch request. Table 8-13 shows extracts from DB2 PE statistics reports for a data sharing environment with two members running the same IRWW workload. Table 8-13 DB2 I/O CI limit removal - Data sharing You can see the positive impact of removing the DB2 CI I/O limits. The number of List Prefetch Reads has reduced, with a corresponding increase in the number of pages read per List Prefetch request. Note also that the number of pages written per write I/O has also increased significantly. This is unique to data sharing and shows the extra benefits of removing this limitation in a data sharing environment. The DB2 CI I/O limits is also removed for castout processing in data sharing environments. The number of pages written per write I/O increased significantly because more pages can now be written in castout. We would also see a corresponding decrease in Unlock Castout requests as reported in the Group Buffer pool Activity section of a DB2 PE Statistics report. Now we have a look at the impact on CPU. Table 8-14 shows CPU times from DB2 PE statistics reports for a non-data sharing environment, running the IRWW workload. Table 8-14 DB2 I/O CI limit removal - Non-data sharing CPU 334 DB2 UDB for z/OS Version 8 Performance Topics 4.76 26.85 Pages Written per Write I/O 1.84 1.83 Activity With I/O CI Limit I/O CI Limit Removed List Prefetch Requests 42,876 42,783 43,186 43,187 List Prefetch Reads 209,600 208,200 40,894 40,711 List Prefetch Pages Read / List Prefetch Reads 3.58 3.56 18.44 18.39 Pages Written per Write I/O 6.20 4.37 27.11 26.49 DBM1 (msec/commit) Total DB2 CPU time (msec/commit) ITR (commits/sec) With I/O CI LImit I/O CI Limit Removed 0.342 0.322 -6% 2.281 2.238 -2% 592.47 601.42 +2% Delta (Removed / With)
8.4.2 Conclusion The values listed show a significant reduction in overall CPU used by the DBM1 address space, (-6%), with a modest increase in transaction throughput, (+2%). This is a result of DB2 performing fewer list prefetch requests for the given workload, as more pages are eligible to be retrieved by each prefetch I/O request. Table 8-15 summarizes CPU times from DB2 PE statistics reports for a data sharing environment, running the same IRWW workload. Table 8-15 DB2 I/O CI limit removal - Data sharing CPU DBM1 (msec / commit) This table combines the effect of both the Locking Protocol changes as well as the removal of the DB2 CI I/O limits on the CPU consumed by the DBM1 address space. Refer to 8.2, “Locking protocol level 2” on page 325, for a discussion on data sharing locking protocol changes in DB2 V8. From Table 8-10 on page 330 we can see the locking protocol changes can account for about a 10% improvement in CPU used by the DBM1 address space. So, by removing the DB2 CI I/O limits in DB2 V8 you can see another modest reduction in CPU used by the DBM1 address space. This is due to fewer list prefetch requests and more efficient castout processing. The removal of the DB2 CI I/O limits for list prefetch requests and castout I/O has the potential to significantly reduce the CPU used by the DBM1 address space. Further benefits can be realized in a data sharing environment through more efficient castout processing. In the past castout processing generally only was able to castout a few pages on each request as pages to be castout can be quite random. With this enhancement castout processing can process more pages for a table space with each request and not be restricted to only pages that are within the 180 CIs within the table space. The extent of CPU gains from this enhancement will vary significantly, depending on application processing, access paths used, data organization and placement. Applications which perform a lot of list prefetch with a large distance between pages will benefit the most from this enhancement. In data sharing, applications which generate a lot of castout processing for not contiguous pages, should also benefit from this enhancement. OLTP performance can definitely experience a positive performance impact from 180 CI limit removal. One customer reported a significant CPU spike every 15 seconds caused by excessive unlock castout and delete namelist requests. This problem was eliminated after the 180 CI limit removal in castout. 8.4.3 Recommendations With I/O CI Limit I/O CI Limit Removed 0.518 0.590 0.456 0.457 -18% Delta (Removed / With) This enhancement is transparent and is available in CM as soon as the PTFs for APARs PQ86071 and PQ89919 have been applied. Chapter 8. Data sharing enhancements 335
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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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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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Page 318 and 319: method. Prior to DB2 V8 those array
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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
Page 330 and 331: DB2 Universal Type 4 Driver - JDBC
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 348 and 349: 7.6.3 Performance The following inf
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Page 352 and 353: Impact on coupling facility: You do
Page 354 and 355: Table 8-1 shows extracts from DB2 P
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Page 368 and 369: 8.5 Miscellaneous items In this sec
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Page 374 and 375: 9.1 Unicode catalog DB2 for z/OS su
Page 376 and 377: that all applications are converted
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Page 380 and 381: From these measurements we observe
Page 382 and 383: Class 1 CPU time (MSEC) 200 150 100
Page 384 and 385: dynamic statement cache. If activat
Page 386 and 387: that everything is ready. This step
Page 388 and 389: Table Number of rows SYSDATABASE 75
Page 390 and 391: In Figure 9-7 we describe the perfo
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Page 394 and 395: Query 35 36 Old DSNTESQ CPU 1 hr 1
Page 396 and 397: 10.1 DB2 Estimator DB2 Estimator V8
Page 398 and 399: - REAL AND AUXILIARY STORAGE This i
Page 400 and 401: Another use is during back out of a
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Page 408 and 409: DSNTIAUL with multi-row fetch The r
Page 410 and 411: A.1 Maintenance for DB2 V8 The APAR
Page 412 and 413: APAR # Area Text PTF and Notes PQ88
Page 414 and 415: APAR # Area Text PTF and Notes PQ96
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APAR # Area Text PTF and Notes PK21
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APAR # Area Text PTF and Notes PQ85
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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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