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

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6.1 Online CHECK INDEX Online CHECK INDEX is a new capability of DB2 V8, added by APARs PQ92749 (PTF UK04683) and PQ96956 (still OPEN), which allows you to have read-write access to applications during CHECK INDEX and contributes to decreasing read-only time for users. This function satisfies the high availability requirement of users with very large tables who cannot afford the application outage caused by the extensive read-only time required to run the normal CHECK INDEX. CHECK INDEX is an online utility which is used to test whether an index is consistent with its data. It is generally useful after a conditional restart or point-in-time recovery. It is also recommended to run CHECK INDEX before CHECK DATA, especially if you specify DELETE YES. Running CHECK INDEX before CHECK DATA ensures that the indexes that CHECK DATA uses are valid. In DB2 V8 the utility statement CHECK INDEX was enhanced to designate the current read-only behavior as SHRLEVEL REFERENCE, and designate a reduction of restricted availability with the new SHRLEVEL CHANGE option. In addition CHECK INDEX provides a parallel processing structure similar to REBUILD INDEX. SHRLEVEL REFERENCE and SHRLEVEL CHANGE There are two options to indicate the type of access that is allowed for objects to be checked during the procedure. Figure 6-1 shows the utility process with the two options. indexes tablespaces UNLOAD phase unload index entries Figure 6-1 CHECK INDEX SHRLEVEL REFERENCE and SHRLEVEL CHANGE If you specify SHRLEVEL REFERENCE, which is also the default, the application can read from but cannot write to the index, table space, or partition that is to be checked. 262 DB2 UDB for z/OS Version 8 Performance Topics CHECK INDEX SHRLEVEL REFERENCE SORT phase Sort index entries Temporary work datasets CHKIDX phase Scan tablespace data to validate CHECK INDEX SHRLEVEL CHANGE SNAPSHOT COPY (e.g., FlashCopy 2) tablespaces tablespaces Shadow dataset Shadow dataset tablespaces tablespaces UNLOAD phase unload from table space to workfile SORT phase Sort index keys MERGE phase Merge index keys (only in NPI) CHKIDX phase Scan index to validate indexes Temporary work datasets indexes
If you specify SHRLEVEL CHANGE, the applications can read from and write to the index, table space or partition that is being checked. The phases of processing inside CHECK INDEX differ in SHRLEVEL REFERENCE and SHRLEVEL CHANGE. In the case of SHRLEVEL REFERENCE, DB2 unloads the index entries, sorts the index entries, and scans the data to validate index entries. On the other hand, SHRLEVEL CHANGE first goes to the table space data set and unloads the data and sorts the index keys and merges (if the index is non-partitioned), and then scans the index to validate. CHECK INDEX with option SHRLEVEL CHANGE performs the following actions: ► Issues QUIESCE WRITE YES for the specified object and all of its indexes (this drains the writers so no updates are allowed for a while) ► Invokes DFSMSdss at the data set level to copy the table space and all indexes to shadow data sets Note: Online CHECK INDEX will use FlashCopy V2 if available, otherwise concurrent copy will be used, this can elongate the read-only time. ► Allows write access to the specified object and indexes ► Runs CHECK INDEX on the shadow data sets Tip: FlashCopy V2 is needed since it supports data set copy (FlashCopy V1 works only at the volume level). Another advantage is that the source and target of a FlashCopy V2 can be a different logical subsystem within the Enterprise Storage System. Index processing with SHRLEVEL CHANGE SHRLEVEL CHANGE has a new architecture. SHRLEVEL REFERENCE unload phase unloads keys from the index and the check phase compares sorted keys against the data via tablespace scan. SHRLEVEL CHANGE unload phase does a table space scan extracting keys and the check phase compares sorted keys against the keys in the index. CHECK INDEX in V8 can provide parallel processing like REBUILD INDEX, which minimizes elapsed time for checking the data and indexes. If you specify more than one index to check and the SHRLEVEL CHANGE option, CHECK INDEX checks the indexes in parallel unless constrained by available memory or sort work files. Checking indexes in parallel reduces the elapsed time for a CHECK INDEX job by sorting the index keys and checking multiple indexes in parallel, rather than sequentially. It is important for parallel processing to specify appropriate values in the SORTDEVT and SORTNUM parameter. SORTDEVT specifies the device type for temporary data sets that are to be dynamically allocated by the DFSORT. SORTNUM can specify the number of temporary data sets dynamically allocated by the sort program (DFSORT). Example 6-1 is a sample JCL of CHECK INDEX. Example 6-1 Sample JCL of CHECK INDEX SHRLEVEL CHANGE //CHKIDXB EXEC PGM=DSNUTILB,REGION=4096K,PARM='SSTR,CHKINDX1' //SYSPRINT DD SYSOUT=A //SYSUDUMP DD SYSOUT=A //UTPRINT DD SYSOUT=A //DSNTRACE DD SYSOUT=A //SYSUT1 DD UNIT=SYSDA,SPACE=(CYL,(5,2)),VOL=SER=SCR03 //SYSOUT DD UNIT=SYSDA,SPACE=(CYL,(5,2)),VOL=SER=SCR03 //SORTLIB DD DISP=SHR,DSN=SYS1.SORTLIB Chapter 6. Utilities 263
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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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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
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
Page 266 and 267: ► CHAR(8) to VARCHAR(8) ► CHAR(
Page 268 and 269: Before ALTER INDEX add column, a ta
Page 270 and 271: 30 25 20 15 10 Figure 5-12 FETCH CP
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
Page 288 and 289: Note that when the qualified partit
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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 310 and 311: cases is the total time of RUNSTATS
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
Page 328 and 329: WebSphere z/OS - DB2 z/OS V8 - Serv
Page 330 and 331: DB2 Universal Type 4 Driver - JDBC
Page 332 and 333: Use DB2 Connect when a high amount
Page 334 and 335: JCC Type 4 Direct 4:3 Concentration
Page 336 and 337: The SYSIBM.INDOUBT table and the pa
Page 338 and 339: Batch updates A batched update is a
Page 340 and 341: Example In DB2 V8 SQL/XML publishin
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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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DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

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