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

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While there is no optimistic locking with the dynamic scrollable cursor model, it is also recommended that CS be used to achieve maximum concurrency. Since dynamic scrollable cursors are most useful for applications that want to see updated rows as well as newly inserted rows, specifying an isolation level of RS or RR restricts updates to the table by other users. 3.12.2 Dynamic scrollable cursor description Dynamic scrollable cursors allow visibility of inserts as well as updates done by you or other users, while static scrollable cursors do not have a visibility to inserts. The differences of dynamic scrollable cursor compared to static scrollable cursor are: ► Accesses the base tables directly ► Inserts done into the base tables are visible ► New options of DECLARE CURSOR statement: – DECLARE CURSOR ASENSITIVE – DECLARE CURSOR SENSITIVE DYNAMIC Dynamic scrollable cursors can be used with row-level or rowset-level operations, so DDF applications should use multi-row FETCH and positioned UPDATE/DELETE for multi-row FETCH. Sensitivity options for dynamic scrollable cursor In this section we show the syntax of the DECLARE CURSOR and FETCH statements associated with the dynamic scrollable cursors. DECLARE CURSOR statement There are some new options in V8 in the DECLARE CURSOR statement to support dynamic scrollable cursors. Figure 3-44 shows the syntax of the DECLARE CURSOR. DECLARE cursor-nam e Figure 3-44 DECLARE CURSOR syntax NO SCROLL is the default and indicates that the cursors are not scrollable. If you specify SCROLL, the cursors become scrollable. ASENSITIVE and SENSITIVE DYNAMIC are new options of scrollable cursors introduced in V8. INSENSITIVE and SENSITIVE STATIC are equivalent to static scrollable cursors in V7. The new two attributes of dynamic scrollable cursors determine the sensitivity of the cursors. ► SENSITIVE DYNAMIC SCROLLABLE 94 DB2 UDB for z/OS Version 8 Performance Topics DECLARE CURSOR NO SCROLL ASENSITIVE IN S E N S ITIV E SENSITIVE STATIC DYNAMIC SCROLL CURSOR FOR select-statement WITH HOLD WITH RETURN statement-name
If you specify this option, the result table of the cursor is dynamic. It means that the size of the result table is not fixed and it may change depending on the changes made against rows in the underlying table after the cursor is opened. All inserts, updates, and deletes by the same application processes through the cursor are immediately visible. Also all positioned updates and deletes are immediately visible even before commit. And inserts and updates and deletes by other applications are visible once committed. No temporary result table is created for SENSITIVE DYNAMIC, since the FETCH statements are executed against the base table. ► ASENSITIVE SCROLLABLE You can use this option, when you let DB2 determine the sensitivity of the cursor. DB2 determines whether the cursor behaves as SENSITIVE DYNAMIC SCROLLABLE or INSENSITIVE (STATIC) SCROLLABLE depending on the update ability of the associated SELECT statement. ASENSITIVE CURSORS may then require TEMP database since they can resolve to INSENSITIVE cursors, depending on the SELECT statement. – The cursor behaves as an INSENSITIVE SCROLLABLE cursor, when the SELECT statement is read-only and does not allow the cursor to be sensitive. In these cases, access to the declared temporary table may be necessary. – The cursor provides maximum sensitivity, which is SENSITIVE DYNAMIC SCROLLABLE, when the cursor is not read-only. It is suitable for client applications that do not care about whether or not the server supports sensitivity. Note: There is no DYNAMIC option for INSENSITIVE. The syntax is SENSITIVE DYNAMIC SCROLLABLE cursor (the query cannot be read-only) or INSENSITIVE SCROLLABLE cursor (the query can be anything, but a temp table may be required for materialization). The current conditions for read-only cursors are listed under Declare Cursor in Chapter 5 of DB2 UDB for z/OS Version 8 SQL Reference, SC18-7426-01. The READ ONLY and FETCH ONLY clauses by themselves do not require a temporary data base. FETCH statement There is no new option in V8 to use dynamic scrollable cursors. All the positioning keywords for fetch (NEXT, PRIOR, FIRST, LAST, CURRENT, BEFORE, AFTER, ABSOLUTE, and RELATIVE) that were introduced in DB2 V7 to support static scrollable cursors are equally relevant for dynamic scrollable cursors. However, there are some restrictions and considerations about the FETCH statement. Figure 3-45 shows the FETCH syntax. Chapter 3. SQL performance 95
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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
Page 76 and 77: the materialized query table. If it
Page 78 and 79: Figure 3-9 MQTs and short running q
Page 80 and 81: ► The elapsed time is 22 times sm
Page 82 and 83: Figure 3-13 Regrouping on MQT resul
Page 84 and 85: EVE.EXT = 'ADD BILL' AND EVE.TXC =
Page 86 and 87: Star Schema Figure 3-15 Star schema
Page 88 and 89: merge joins and work file usage. DB
Page 90 and 91: Star join access path without a spa
Page 92 and 93: 3.3.4 Performance Sparse index for
Page 94 and 95: V8 Star Join Access Path Figure 3-2
Page 96 and 97: 3.3.5 Conclusion Star join workload
Page 98 and 99: . SELECT * FROM PAOLO.TORDER WHERE
Page 100 and 101: But not all mismatched numeric type
Page 102 and 103: V8 shows that PL is joined with CV
Page 104 and 105: Query performance problem Lack of m
Page 106 and 107: 3.5.1 Performance SORTDEVT SYSDA IN
Page 108 and 109: 3.5.2 Conclusions Figure 3-31 Acces
Page 110 and 111: Mismatched data types SELECT COUNT(
Page 112 and 113: 3.7.1 Performance In V8 the paralle
Page 114 and 115: 3.7.2 Conclusions Example 3-9 Multi
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Page 118 and 119: 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 128 and 129: FETCH FROM Figure 3-45 FETCH syntax
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Page 132 and 133: application has decidedly higher Cl
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Page 136 and 137: Multi-row FETCH with a static curso
Page 138 and 139: 3.12.5 Conclusion Multi-row FETCH a
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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
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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 170 and 171: However, the combined impact of oth
Page 172 and 173: Frees up space below the bar for ot
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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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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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