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

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C.1 DB2 SQL PA additional reports Notice that the index used has a NOT PADDED attribute and a cartesian join was detected. Example C-1 reports the query definition and also some good news for the query. Example: C-1 SQL PA query description ================================================================================ SQL PA ANALYSIS FOR QUERYNO 100000001 SELECT COUNT(*) FROM SYSIBM.SYSPACKSTMT A, SYSIBM.SYSPACKDEP B WHERE A.LOCATION = ? AND B.DLOCATION = ? AND B.DCOLLID = ? AND A.COLLID ? QUERYNO: 100000001 QBLOCKNO: 1 PLANNO: 1 MIXOPSEQ: 0 PROCESS -> +------------------------------------------------------------------+ |ANL7002I *** GUIDELINE: | |This plan step has not selected any Sequential|List Prefetch I/O. | |If the SQL processes just a few rows that is OK, but if many rows | |are involved, you can help promote Sequential Detection by both | |accessing the data in sequential order (presort?) and by binding | |with Release (Deallocate) to avoid resetting counters at Commit. | +------------------------------------------------------------------+ +------------------------------------------------------------------+ |ANL7005I *** GOOD NEWS: | |This SQL features a Unique Index being used to access the table | |that can avoid Distinct Sorts with Group By and Count Distinct C1.| |Also, unique index will avoid 4K "in memory table" on Correlated | |Subquery, considers special access path when used with "=" preds, | |and may convert Subquery to Join on IN, =ANY or =SOME predicates. | +------------------------------------------------------------------+ +------------------------------------------------------------------+ |ANL6005I *** NOTE: | |This statement contains a Built in Column Function: however, it | |is not being processed at either Stage 1 Retrieval or Sort Time. | |In general, this means poor performance, because the column(s) get| |evaluated only at the end of Stage 2 processing. This might be due| |to multiple columns used, Group By, not all Stage 1 preds, etc. | +------------------------------------------------------------------+ Example C-2 provides information about the indexes. Example: C-2 SQL PA index information ACCESS IS VIA THE CLUSTERING (INSERT & LOAD ORDER) INDEX FOR THIS TABLE +------------------------------------------------------------------+ |ANL5018W *** ALERT: | 400 DB2 UDB for z/OS Version 8 Performance Topics
|This clustering (insert) index has a low cluster ratio (below 80) | |and/or is not well clustered (Clustered flag = N), meaning that | |inserts are following an unclustered pattern: this is not helpful.| |You should Reorganize your Table and Index, and re-run Runstats to| |update these statistics. That should result in better access paths| |and performance in general. | +------------------------------------------------------------------+ RANDOM MATCH IX SCAN -------------------- IX CREATOR: SYSIBM INDEX NAME: DSNKSX01 VERS: 1 KEY LEN: -1 PADDED: N C-ED: N C-ING: Y CLURATIO: 10.0000 FULLKEY CARD: 25 FIRSTKEY CARD: 25 TYPE: 2 NLEAF PAGES: 34 NLEVELS: 2 UNIQUE: U DECLARE UNIQ 1 OF 5 COLUMNS ARE MATCHED CLOSE: N LOCK MODE: IS BPOOL: BP0 KEY COLUMN NAME ORDER TYPE DIST LEN NULL COLCARD DIST# ------------------------------------------------------------------------ 1 LOCATION A VARCHAR N 128 N -1 0 2 COLLID A VARCHAR N 128 N -1 0 3 NAME A VARCHAR N 128 N -1 0 4 CONTOKEN A CHAR N 8 N -1 0 5 SEQNO A SMALLINT N 2 N -1 0 +------------------------------------------------------------------+ |ANL6052I *** NOTE: | |This index is specified as "Not Padded", allowing storage of a | |varying length index key. Padded indexes use blanks to fill out | |their fixed length keys and are not eligible for Index Only scan. | |"Not Padded" indexes do not blank fill CHAR and VARCHAR columns, | |allowing greater flexibility and better use of storage, packing | |more entries into a single Leaf page. Index Only access allowed. | +------------------------------------------------------------------+ NOTE: NO ALTERNATIVE INDEXES AVAILABLE FOR THIS TABLE +------------------------------------------------------------------+ |ANL6016I *** NOTE: | |Presently this query is only matching some of the indexed columns | |on this index key. Maximizing use of Stage 1 predicates against | |these index columns will improve performance, by matching and/or | |screening rows and therefore reducing data page I/O requirements. | +------------------------------------------------------------------+ +------------------------------------------------------------------+ |ANL7034I *** GOOD NEWS: | |This index is Not Padded, making it a true variable length index. | |"Index Only" access is now possible and DB2 will compare CHAR and | |VARCHAR columns of unequal length against this index during Stage | |1 processing. | +------------------------------------------------------------------+ +------------------------------------------------------------------+ |ANL7009I *** GUIDELINE: | |On composite (multi-column) indexes, favor matching index scan of | |as many columns as possible, using Equals (=), Range (>,,
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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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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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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
Page 402 and 403: In DB2, the IBM Data Encryption too
Page 404 and 405: The utilities ran on a G7 Turbo wit
Page 406 and 407: time Figure 10-1 DB2 HPU vs. UNLOAD
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 416 and 417: APAR # Area Text PTF and Notes PK21
Page 424 and 425: 392 DB2 UDB for z/OS Version 8 Perf
Page 426 and 427: B.1 DB2 PE Storage Statistics trace
Page 428 and 429: Storage heading Description 24 BIT
Page 434 and 435: |is the last matching predicate. Ap
Page 436 and 437: |ANL6052I *** NOTE: | |This index i
Page 438 and 439: PREDICATE ANALYSIS ----------------
Page 440 and 441: D.1 DB2 EXPLAIN EXPLAIN describes t
Page 442 and 443: Table D-2 PLAN_TABLE contents and b
Page 444 and 445: Column Type Content SORTC_ORDER BY
Page 446 and 447: Column Type Content OPTHINT CHAR(8)
Page 448 and 449: D.1.3 DSN_FUNCTION_TABLE You can us
Page 450 and 451: Example: D-1 Creating DSN_STATEMENT
Page 452 and 453: Column Type Content BIND_QUALIFIER
Page 456 and 457: ICF integrated catalog facility ICF
Page 458 and 459: ► DB2 UDB for z/OS V8: Through th
Page 462 and 463: character set 174 CHECK DATA 262 CH
Page 464 and 465: Equi-join predicates 54, 402 Equiva
Page 466 and 467: MINSTOR 145-146 Mismatched data typ
Page 468 and 469: PQ84160 378, 387 PQ85764 387 PQ8584
Page 470 and 471: Sort tree nodes 144 SORTDATA 268 SO
Page 472 and 473: 306 Universal Driver for SQLJ and J
Page 476: DB2 UDB for z/OS Version 8 Performa
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DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

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