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

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However, the combined impact of other V8 enhancements in data sharing (for example, CF Request Batching for castout processing and Locking Protocol Level 2 which also reduce the overall SRB CPU time), offsets the increase in CPU times seen by the Accounting class 2 reports and produces a lower percentage increase in CPU overall. Important: Do not just take the accounting class 2 CPU times to compare V7 to V8 performance. You must also factor in any CPU time reduction in the DB2 address spaces from statistics reports. 4.1.3 Recommendations Even though we have found that the relative overhead of running DB2 V8 in NFM is negligible compared to CM and the extra cost of running a DB2 V7 bound plan/package in V8 is also negligible compared to V7, the following recommendations still apply. Unless you go to NFM immediately, consider rebinding your plans and packages in V8 CM as soon as you are comfortable you will not fallback to V7. This gives DB2 the opportunity to select a better access path which potentially benefits your SQL performance, especially for more complex queries. The DB2 Optimizer progressively becomes smarter and smarter with each new release of DB2. You are able to experience the real V8 performance. Tuning for CPU usage in V8 It you were virtual storage constrained in V7 and took initiatives to resolve the virtual storage problems, you may choose to reconsider these initiatives in V8. Some of these actions taken to reduce virtual storage usage have a cost of additional CPU. You may no longer need to have these initiatives in place in V8, since you are less likely to be constrained by storage in V8: ► Increase again the size of buffer pools and other pools you reduced in V7, to once again improve overall performance. ► Consider rebinding some critical plans and packages with RELEASE(DEALLOCATE) again, only if you were using this bind parameter to improve performance of some key applications in V7. (Remember, however, there is less of a need to have plans and packages bound with RELEASE(DEALLOCATE) in DB2 V8 data sharing than V7 data sharing. See Chapter 8, “Data sharing enhancements” on page 319 for a more detailed discussion of why RELEASE(DEALLOCATE) is less necessary in V8.) ► Consider turning on thread reuse again, to improve performance of your critical applications. ► Consider turning off the DSNZPARM EDMBFIT parameter which concerned EDM pool space. ► Consider turning off the DSNZPARM CONTSTOR parameter which regularly contracts thread local storage pools. ► Consider turning off the DSNZPARM MINSTOR parameter which changes the way DB2 allocates local storage for thread use. Other options with significant potential to offset a possible increase in CPU include: ► Rebind all your plans and packages. See the above discussion. ► Long term page fixing your buffer pools This is a strong recommendation as it has the potential to save a much as 8% in CPU. However, only consider this if you have enough real storage available to back 100% of 138 DB2 UDB for z/OS Version 8 Performance Topics
your buffer pools. We recommend you implement long term page fixing, buffer pool by buffer pool, for I/O intensive profiles. See 4.5, “Buffer pool long term page fixing” on page 169, for a more detailed discussion on long term page fixing. ► Multi-row FETCH and INSERT Although this DB2 V8 enhancement requires you to modify your application, it has a significant potential to save CPU cycles. See the sections on Multi-row FETCH and INSERT in Chapter 3, “SQL performance” on page 29 for more details. 4.2 Virtual storage constraint relief DB2 V8 exploits 64-bit storage in the DBM1 address space which provides significant virtual storage constraint relief (VSCR). By way of background, MVS addressing is represented in the power of 2 closest to the corresponding power of 10. Refer to the z/Architecture Principles of Operation, SA22-7832 for a more detailed discussion. 2#10 Kilo (1024 bytes) 2#20 Mega (1024 * 1024 bytes) 2#30 Giga (1024 * 1024 * 1024 bytes) 2#40 Tera (1024 * 1024 * 1024 * 1024 bytes) 2#50 Peta (a really big number) 2#60 Exa (an even bigger number) 2#70 Zetta (too big a number) 2#70 Yotta (the “Restaurant at the end of the Universe!”) So 2#64 is 16EB -- and the largest z/Architecture address is 16E-1. DB2 now supports a 16-exabyte DBM1 address space. A 16-exabyte address space is 8 billion times larger than a 2-gigabyte (GB) address space. The new virtual storage area above the old 2 GB limit is referred to as above the bar. Figure 4-3 provides a simplified introductory description of the major storage areas that have moved above the 2 GB bar in the DBM1 address space. The 64-bit storage exploitation in DB2 V8 provides a number of performance improvements to DB2 which we discuss in this section. The entities which have been moved above the bar in the DB2 V8 DBM1 address space include: ► 64-bit virtual buffer pool and their control blocks Larger buffer pools enable I/O reduction for random access, and enable larger page sizes which benefit sequential access. Buffer pool management is also made simpler. ► DBDs in the EDM pool More database objects can be defined and I/O to the DB2 directory is reduced because the pool can be larger. ► EDM statement cache A larger cache may avoid dynamic SQL PREPAREs. ► Compression dictionaries You no longer need to manage the open and close for table spaces to manage the amount of DBM1 storage which is required by compression dictionaries for open compressed table spaces. ► Sort pools Chapter 4. DB2 subsystem performance 139
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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
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
Page 132 and 133: application has decidedly higher Cl
Page 134 and 135: Static updatable cursor You can see
Page 136 and 137: Multi-row FETCH with a static curso
Page 138 and 139: 3.12.5 Conclusion Multi-row FETCH a
Page 140 and 141: While, for or SELECT ... FROM ...
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
Page 154 and 155: The Plug-In Options screen of Stati
Page 156 and 157: Before the introduction of MQTs, DB
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Page 160 and 161: ► Larger VSAM CI sizes: DB2 V8 in
Page 162 and 163: 4.1.1 Performance support caused al
Page 164 and 165: Regression is about 5% better than
Page 166 and 167: The results indicate no significant
Page 168 and 169: Important: 4.1.2 Conclusion If you
Page 172 and 173: Frees up space below the bar for ot
Page 174 and 175: from the hiperpools, they were not
Page 176 and 177: So, we advise you to not overalloca
Page 178 and 179: See 4.3, “Monitoring DBM1 storage
Page 180 and 181: Table 4-4 System storage configurat
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Page 184 and 185: KB 600 500 400 300 200 100 0 Figure
Page 186 and 187: For the same buffer pool size and o
Page 188 and 189: 4.2.3 Conclusion Nondistributed per
Page 190 and 191: Important: With PTFs UK04394 (DB2 V
Page 192 and 193: - DATASPACE BP CONTROL BLOCKS = 0 M
Page 194 and 195: The EXTENDED REGION SIZE (MAX) is t
Page 196 and 197: RDS OP POOL (MB) N/A RID POOL (MB)
Page 198 and 199: As you can now appreciate, it is im
Page 200 and 201: Megabytes A V7 Customer DBM1 Thread
Page 202 and 203: 4.5.1 Performance The most buffer p
Page 204 and 205: 4.6.1 Performance maintained in a 2
Page 206 and 207: 4.6.2 Conclusion We can conclude th
Page 208 and 209: service for Unicode conversions, an
Page 210 and 211: overcome this, when DB2 Connect is
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Page 214 and 215: AIX C-program Conversion Routines P
Page 216 and 217: 4.7.1 Performance The improvements
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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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216 DB2 UDB for z/OS Version 8 Perf
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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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