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

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overcome this, when DB2 Connect is interfacing with DB2 for z/OS V7, DB2 Connect sends the data in Unicode (by default). If you still require the data to be sent in ASCII instead of Unicode, then you may set the DISABLEUNICODE=1 parameter. DISABLEUNICODE is specified in the db2cli.ini file. Older z/OS systems were slow to convert Unicode so it was desirable to specify DISABLEUNICODE=1. Otherwise, installations migrating from DB2 for z/OS V6 to V7 would experience an increase in class 2 CPU time. Only for Java Applications was it preferable not to specify DISABLEUNICODE=1. This performance problem goes away with z/OS 1.4, because now Unicode conversion is faster than ASCII conversion. Furthermore, if the database is actually stored in Unicode, setting DISABLEUNICODE adds Unicode conversions to the class 2 CPU time. In the above example, the DB2 Connect properties file indicates DISABLEUNICODE=1, which prevents DB2 Connect from sending data as Unicode. The data sent on INSERTS is in ASCII. The DBM1 address space converts the ASCII data to Unicode. For the SELECT statement, DB2 Connect on the client converts the data from Unicode back to ASCII. Only those conversions done by the DIST address space are counted as class 2 CPU time. Class 2 CPU time is unaffected by the conversions done by the client, but if the client is running locally on z/OS, the CPU time for conversions done by the client may be part of class 1 CPU time. Conversions done by a non-z/OS client do not use zSeries mainframe resources. Figure 4-14 shows the effect of not disabling Unicode in DB2 Connect, which is the default. C-program INSERT HV1 943 HV2 943 SELECT HV1 943 HV2 943 DB2 Connect V8 Conversion Routines Figure 4-14 CCSID conversion - Remote application - 2 In this case, DB2 Connect sends all data as 1208, no matter what the type of column is. The DB2 for z/OS conversions for CHAR columns disappear. However, there is a double conversion for GRAPHIC columns, but only the second conversion is done by DB2 for z/OS. 178 DB2 UDB for z/OS Version 8 Performance Topics DisableUnicode=0 AIX z/OS DRDA Common Layer DDF DB2 for z/OS DBM1 1208 COLC 1200 COLG 1208 COLC 1200 COLG
Still, this second conversion is a conversion from 1208 to 1200 which is somewhat less expensive than an ASCII conversion (provided that z/OS 1.4 is installed). In summary, for CHAR columns, not setting DISABLEUNICODE shifts the Unicode conversion during the Insert from the z/OS server to the workstation client, helping to reduce class 2 CPU time. For GRAPHIC columns, DISABLEUNICODE has a more subtle effect, because in one case the class 2 CPU time contains a conversion from UTF-8 to UTF-16, and in the other case the class 2 CPU time contains a conversion from ASCII to UTF-16 (a Java application would send all data as UTF-8.) The same DISABLEUNICODE parameter affects both host variables and SQL statements. Since DB2 V8 does SQL parsing in Unicode, it becomes more important to avoid setting DISABLEUNICODE. This is especially true if any of the code points used in the SQL statement is greater than 127. If all code points are less than 128, CCSID 1208 is equivalent to ASCII, and no conversion of the SQL statement actually occurs. See “DB2 V8 major and minor conversion” on page 185 for more details. Now let us have a look at Unicode conversion for Java clients. Along with DB2 V8, IBM introduced the Universal Driver for JDBC and SQLJ to replace the old Legacy JDBC Driver. The Universal Driver does not use DB2 Connect. The Universal Driver supports both a Type 2 and Type 4 Driver. While the Type 2 Driver is optimally used by local Java applications running on z/OS, the Type 4 Driver can be used by workstation clients as well as z/OS clients. The Type 4 Driver uses DRDA protocols. Since the Universal Driver does not use DB2 Connect, the DISABLEUNICODE parameter is not applicable. Instead the Universal Type 4 Driver supports a new “UseServerEncoding” data source property. Unlike the Legacy Driver, the Universal Driver always sends the SQL statement in UTF-8 no matter how the property is set. The Universal Java Driver is shipped with DB2 V8 and V7 with PQ8841. Although it can connect to DB2 V7, it is optimized to work with DB2 V8. Since the Universal Driver always sends the SQL statement in UTF-8, a V7 server has to convert the SQL statement to EBCDIC, and the result is higher class 2 CPU time. Because there is no disadvantage to using UseServerEncoding=1, our discussion assumes that UseServerEncoding=1 is always used. Figure 4-15 shows the Universal Java Type 2 Driver locally connecting to DB2 V8, first using an EBCDIC database and then using a Unicode database. Chapter 4. DB2 subsystem performance 179
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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
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 170 and 171: However, the combined impact of oth
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
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Page 214 and 215: AIX C-program Conversion Routines P
Page 216 and 217: 4.7.1 Performance The improvements
Page 218 and 219: In October 2003, a new enhancement
Page 220 and 221: UseServerEncoding data source prope
Page 222 and 223: 4.8.1 Performance 4.8.2 Conclusion
Page 224 and 225: Multilevel security with row-level
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Page 230 and 231: 4.9.2 Conclusion The CPU increase c
Page 232 and 233: 4.10.1 Performance VSAM does not kn
Page 234 and 235: 4.10.2 Conclusion 4.10.3 Striping A
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Page 240 and 241: This message is completed with the
Page 242 and 243: This enhancement is introduced by P
Page 244 and 245: This record is activated by: -START
Page 246 and 247: an online transaction with very sim
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Page 250 and 251: 5.1 System level point-in-time reco
Page 252 and 253: BACKUP SYSTEM During backup DB2 rec
Page 254 and 255: Figure 5-1 FRBACKUP PREPARE elapsed
Page 256 and 257: Figure 5-4 BACKUP SYSTEM FULL measu
Page 258 and 259: 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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