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

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Note that when the qualified partitions cannot be determined at BIND time because the literal value in the predicate is unknown (for example, because a host-variable, parameter marker, or special register is used), then DB2 will determine what the qualified partitions are at execution time. By doing this, only the qualified partitions will be accessed, even if DB2 could not determine which partitions were qualified at BIND time. (This enhancement does NOT require the use of REOPT(VARS)). In addition, the DB2 access path selection has been enhanced to make use of all leading partitioning key columns when determining the qualified partitions. (Currently, only the first column of the partitioning key is used to determine which partitions qualify. This can result in more partitions being in the range of qualified partitions than actually do qualify.) This enhancement will not only benefit cases that use a DPSI to access the data, but any case where a partitioned table space was accessed with too many partitions qualified. 5.6 Other availability enhancements Other DB2 V8 availability enhancements and also recent enhancements introduced via maintenance are discussed in this section. 5.6.1 More online DSNZPARMs In order to minimize downtime when making DSNZPARM parameter changes effective, DB2 V7 introduced the online change for subsystem parameters. This function allows you to load a new subsystem parameter load module into storage without recycling DB2. To do this, you can use the normal installation parameter update process to produce a new load module, which includes any desired changes to parameter values. You can then issue the -SET SYSPARM command to load the new module in order to affect the change. DB2 V8 adds more online changeable parameters. Not all subsystem parameters are dynamically changeable. Refer to the Appendix of DB2 UDB for z/OS Version 8 DB2 Command Reference, SC18-7416, for a list of all parameters, the macros where they are defined, and whether or not they are changeable online. 5.6.2 Monitor long running UR back out During restart processing, DB2 issues progress messages during the forward and backward phase of the restart. Message DSNR031I is issued in 2 minute intervals, showing the current log RBA being processed and the target RBA to complete the restart phase. With DB2 V8, a new progress message is issued during the back out of postponed URs as well. This message is first issued after the process has at least exceeded one two minute interval and is repeated every two minutes until the back out process is complete. 5.6.3 Monitor system checkpoints and log offload activity With DB2 V7, you had the chance to monitor the actuality of system checkpoints and the status of the log offload activity using DB2 command -DISPLAY LOG, which was introduced to DB2 V6. Sometimes, however, there are situations where DB2 stopped taking system checkpoints or was stuck during its log offload activity. Since both situations might cause problems during operations, DB2 V8 provides you with new messages, which help you identify problems faster. In addition a new IFCID 0335 record is produced if a statistics class 3 is active. 256 DB2 UDB for z/OS Version 8 Performance Topics
5.6.4 Improved LPL recovery One source of unplanned outages that many DB2 customers have struggled with is LPL (logical page list) pages. DB2 puts pages into the LPL typically when I/O or coupling facility read or write errors are encountered. Once a page is entered into the LPL, that page is inaccessible until it is recovered. LPL recovery can be done using: ► -START DATABASE command with SPACENAM option ► RECOVER utility The -START DATABASE command drains the entire table space or partition, therefore making the entire page set or partition unavailable for the duration of the LPL recovery process even if only one page is in the LPL for that table space or partition. During the execution of the recover utility the table space or partition is unavailable. DB2 V8 always attempts to automatically recover the LPL pages at the time that the pages are added to LPL. Those pages are deleted from the LPL when the automatic LPL recovery completes successfully. Even more important than automatic LPL recovery is that with DB2 V8, during LPL recovery, all pages that are not in the LPL are accessible by SQL. Up to DB2 V7, the entire table space or partition was unavailable during LPL recovery. 5.6.5 Partitioning key update enhancement Some customers find the current implementation that allows update of values in partitioning key columns unusable because it does not allow concurrency if an update of a partitioning key changes the partition to which the row belongs. If the update requires moving the data row from one partition to another, DB2 tries to take exclusive control of the objects to perform the update by acquiring DRAIN locks. Because of this, no other application can access the range of partitions affected by update of values in partitioning key columns. Description Up to DB2 V7, DB2 takes the exclusive control to perform the partitioned key update on: ► The partition of the table space from which the row is moving, the partition of the table space to which the row is moving, and all partitions in between, ► The partition of the partitioning index from which the partitioning key is moving, the partition of the partitioning index to which the partitioning key is moving, and all partitions in between ► Non partitioning indexes defined on the table space. When updating values in columns that define the partitioning key, DB2 V8 will NOT take exclusive control of the objects to perform the update. If a row moves from one partition to another in a table that is a dependent table in a Referential Integrity relationship, there is a possibility of missing the row when checking for RI. To prevent this, if any update changes the row’s partition, a COMMIT duration S lock will be acquired on the parent table rows. Change to DSNZPARM parameter PARTKEYU The existing system parameter PARTKEYU specifies whether values in columns that participate in partitioning keys may be updated. ► “YES” - Values in such columns may be updated. This is the default value. Chapter 5. Availability and capacity enhancements 257
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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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Page 250 and 251: 5.1 System level point-in-time reco
Page 252 and 253: BACKUP SYSTEM During backup DB2 rec
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Page 258 and 259: 5.1.2 Conclusion The BACKUP SYSTEM
Page 260 and 261: Figure 5-7 shows the sliding scale
Page 262 and 263: Maybe you have implemented a space
Page 264 and 265: For dynamically prepared queries, D
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Page 268 and 269: Before ALTER INDEX add column, a ta
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Page 272 and 273: Percent of index pages Avg. Index L
Page 274 and 275: 300 250 200 time in seconds 150 100
Page 276 and 277: REORG REBALANCE We executed and mea
Page 278 and 279: 5.4 Volatile table 5.4.1 Conclusion
Page 280 and 281: If explicit clustering for a table
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Page 286 and 287: RUNSTATS INDEX PARTITION of a DPSI
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Page 298 and 299: - SORT 6 indexes in parallel - CHEC
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Page 302 and 303: 6.3 LOAD and UNLOAD delimited input
Page 304 and 305: 6.3.2 Conclusion We measured the CP
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Page 312 and 313: 6.4.5 Conclusion Statistics Advisor
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Page 322 and 323: 7.2.2 Performance - Distributed cli
Page 324 and 325: Recommendation If you currently do
Page 326 and 327: ► The DB2 Universal JDBC type 4 D
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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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