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

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Volatile (or cluster) tables, used primarily by ERP vendors like SAP, are tables that contain groups (or clusters) of rows which logically belong together. Within each cluster, rows are meant to be accessed in the same sequence every time. Lock contention occurs when DB2 chooses different access paths for different applications operating on the same cluster table. In the absence of support for cluster tables in DB2, users have to either change system-wide parameters that affect all tables, or change statistics for each such table to ease the lock contention. Cluster tables are referred to as volatile tables in DB2. Adding a new keyword, VOLATILE, to the CREATE TABLE and ALTER TABLE statements signifies to DB2 which tables should be treated as volatile tables. For volatile tables, index access is chosen whenever possible, regardless of the efficiency of the available indexes. That is, a table scan is not chosen in preference to an inefficient index. – CF lock propagation reduction In a data sharing environment, this enhancement allows parent L-locks to be granted locally without invoking global contention processing. Thereby, locking overhead due to false contention is reduced. As a result, DB2 data sharing performance is enhanced. Performance benefit varies depending on factors such as commit interval, thread reuse, and number of tables accessed in a commit interval, if the SQL processing is read-only or update. – Several other lock enhancements, including overflow lock avoidance, skip uncommitted inserts, and drain lock on partition key update. ► Instrumentation enhancements DB2 V8 comes with numerous enhancements to the Instrumentation Facility Interface. The most important are: – Package level accounting – Accounting roll-up for DDF and RRSAF threads – Long-running reader tracking – Lock escalation trace record – Full SQL statement text trace record – PREPARE attributes are also traced – More high water marks in the statistics record – Secondary authorization IDs via READS – Storage 64-bit support as well as READS support – Temporary space usage – Auditing for multilevel security – Option for EBCDIC or Unicode data 1.1.5 Migration changes Migration is allowed exclusively from DB2 V7 subsystems. The migration SPE must have been applied and started. The migration process has been changed and now consists of three distinct steps or phases: 1. Compatibility mode (CM): This is the first phase, during which the user performs all the tests needed to make sure all the applications run without problems with the new version. Fallback to V7 in case of problems is allowed. 2. Enabling-new-function mode (ENFM): During this typically short (usually one hour) second phase, the user converts the DB2 catalog and directory to a new format by using online REORG executions. No fallback to DB2 V7 is allowed once this phase is entered. 3. New-function mode (NFM): This is the target third and final phase, where all new V8 functions are available. 8 DB2 UDB for z/OS Version 8 Performance Topics
Chapter 2. Performance overview 2 Scalability, availability, and performance are key reasons to choose DB2 as your premier enterprise database server. These reasons are mandatory criteria for DB2 in order to allow growth and be able to exploit (in a balanced manner) increasing processor speed, larger central storage and faster I/O devices. However, two major inhibitors slowed down growth for some leading edge users. These inhibitors were the size of virtual storage available per address space and the persistent difference in speed between processors and disks’ service time. The 2 GB virtual memory size, dictated by the 31-bit MVS architecture, was an inhibitor to growth for the DBM1 address space where many DB2 throughput-related pools were acquired. This limited addressing capability in turn reduced the size of the buffer pools that could be assigned for accessing data. The theoretical limit for the virtual buffer pools is 1.6 GB, but realistically, for most high-end customers, it is less than 800 MB, regardless of the availability of real storage. DB2 V7 customers, needing a larger buffer pool, likely use data space buffer pools, and are able to use 10 to 20 GB. The architectural solution DB2 V8 provides is to adopt the 64-bit z/OS architecture and remove the major storage inhibitors. Both the DBM1 and IRLM address spaces now run in 64-bit addressing and take advantage of new 64-bit instructions of the zSeries architecture. This allows DB2 to move several storage pools above the 2 GB bar and provides customers virtual storage constraint relief. In turn, this allows exploitation of the processor speed and usage of the real storage size of the largest systems. Savvy users are cautious about changing long-established capacity rules and will ask you pertinent questions similar to the following ones: ► What is the impact of the new architecture in terms of CPU and I/O utilization? ► How is the virtual storage layout changing? What is still below the 2 GB bar, and what has moved above the bar? ► How can I make sure I have enough real storage to support my workload today, and tomorrow? ► What else needs to be done to take advantage of the architecture? ► What new DSNZPARMs affect my real storage consumption? ► What old DSNZPARM default settings may have changed to affect storage and CPU considerations? © Copyright IBM Corp. 2005. All rights reserved. 9
Page 1: ibm.com/redbooks Front cover DB2 UD
Page 4 and 5: Note: Before using this information
Page 6 and 7: 2.5.3 Increased number of deferred
Page 8 and 9: 4.5.2 Conclusion . . . . . . . . .
Page 10 and 11: 7.4.1 ODBC Unicode support . . . .
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Page 14 and 15: 3-48 Consistency query - 31 New . .
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Page 18 and 19: 8-5 CF Request Batching - DB2 CPU .
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Page 22 and 23: Trademarks The following terms are
Page 24 and 25: Added information The following APA
Page 26 and 27: ► Added reference to June 15, 200
Page 28 and 29: Michael Parbs is a DB2 Specialist w
Page 30 and 31: Hugh Smith Jim Teng John Tobler Yoi
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Page 34 and 35: 1.1 Overview 1.1.1 Architecture IBM
Page 36 and 37: - Column data type changes can be d
Page 38 and 39: 1.1.3 Data warehouse 1.1.4 Performa
Page 42 and 43: In this chapter we anticipate the a
Page 44 and 45: 2.1.3 I/O time 2.1.4 Virtual storag
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Page 48 and 49: application that can have great pot
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Page 58 and 59: Macro Parameter Old value New value
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Page 62 and 63: ► Parallel sort enhancement Paral
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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
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Page 76 and 77: the materialized query table. If it
Page 78 and 79: Figure 3-9 MQTs and short running q
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Page 82 and 83: Figure 3-13 Regrouping on MQT resul
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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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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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