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

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Maybe you have implemented a space allocation strategy at your site. You do not have to alter your current strategy in order to benefit from the automated secondary quantity space management. Specifying MGEXTSZ=YES triggers DB2 to manage the size of secondary allocations by the sliding scale mechanism. This guarantees that you will never run out of extents and still honors the SECQTY that you specified if greater than the DB2 calculated value. 5.3 Online schema Note: PTF UK08807 for APAR PK0564 provides a data set preformat quantity adjustment to take into account the larger sizes of secondary extents. In the past, DB2 releases have implemented most DDL ALTER enhancements without actively addressing the problem of data unavailability while modifying object attributes. Some schema changes could already be done without having to drop and recreate an object, or stopping and starting the object, such as adding a column to a table, renaming a table, altering the primary and secondary quantity of an object, or changing partition boundaries. But many changes to table, table space, and index schemas (DDL) prior to DB2 V8 require that you adhere to the following procedure to implement them: – Unload the data, extract the DDL and authorizations of the object you are about to change, and all dependent objects, like tables, indexes, views, synonyms, triggers, and so on. – Drop the object. – Create the object with the new definition and reestablish authorizations for the object. – Recreate all dependent objects, such as views and indexes, and so forth, and their authorizations. – Reload the data. – Rebind plans and packages. – Test that all is OK. Without the use of DB2 administration tools, this is a cumbersome and error prone process. DB2 V8 allows many more schema changes without having to drop and recreate the objects. 5.3.1 Changing attributes Online schema evolution allows for table space, table and index attribute changes while minimizing impact on availability. The following schema changes are allowed in DB2 V8: Alter column data type Column data types can be changed without losing data availability. ► Increase column size within a data type ► Change the data type After the change: ► The table space is placed in Advisory Reorg Pending (AREO*) state. 230 DB2 UDB for z/OS Version 8 Performance Topics
► The data is accessible but until the table space is reorganized a performance penalty is paid. ► Plans, packages and cached dynamic statements referring to the changed column are invalidated. If auto-rebind is enabled, the plans and packages referencing the changed table space are automatically rebound during the next access if not manually rebound previously. ► Frequency statistics for columns are invalidated. ► The new column type must be large enough to hold the maximum value possible for original column. ► If indexed, changes for character data type columns result in immediate index availability. This includes columns defined as CHAR, VARCHAR, GRAPHIC, or VARGRAPHIC. ► If indexed, changes for numeric data type columns are immediate with delayed index availability. This includes columns defined as SMALLINT, INTEGER, DECIMAL or NUMERIC, FLOAT, REAL, or DOUBLE. Availability to the index is delayed until the index is rebuilt. ► Scope of unavailability for dynamic SQL – Deletes are allowed for table rows, even if there are indexes in RBDP. – Updates and inserts are allowed for table rows, even if their corresponding non-unique indexes are in RBDP state. – Inserting or updating data rows which result in inserting keys into an index that is in RBDP state is disallowed for unique or unique where not null indexes. – For queries, DB2 does not choose an index in RBDP for an access path. Recommendations When using this feature, make sure that you do not forget to assess which programs need to be changed. Host variables, for example, may need to be extended to cater to the extra length. To minimize any performance degradation, schedule a REORG as soon as possible after ALTER. This reestablishes fast column processing and eliminates the conversion from old row format to the new one when retrieved by the application. Rebuild any affected indexes and rebind plans and packages. Otherwise DB2 might pick an inefficient access path during automatic rebind because the best suited index is currently not available. Schedule RUNSTATS to repopulate the catalog with accurate column and index statistics. Alter index Several changes can now be implemented via the ALTER INDEX statement: ► Add a column to the end of an index Adding the column to the table and index in the same UOW will place the index in AREO* state. The index is immediately available. Adding an existing column to the index places the index in rebuild pending (RBDP) status. ► Scope of unavailability for dynamic SQL Deletes are allowed for table rows, even if there are indexes in RBDP. Updates and inserts are allowed for table rows, even if their corresponding non-unique indexes are in RBDP state. Inserting or updating data rows which results in inserting keys into an index that is in RBDP state is disallowed for unique or unique where not null indexes. Chapter 5. Availability and capacity enhancements 231
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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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Page 216 and 217: 4.7.1 Performance The improvements
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Page 222 and 223: 4.8.1 Performance 4.8.2 Conclusion
Page 224 and 225: Multilevel security with row-level
Page 226 and 227: ► The security level that defines
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Page 230 and 231: 4.9.2 Conclusion The CPU increase c
Page 232 and 233: 4.10.1 Performance VSAM does not kn
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Page 240 and 241: This message is completed with the
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Page 250 and 251: 5.1 System level point-in-time reco
Page 252 and 253: BACKUP SYSTEM During backup DB2 rec
Page 254 and 255: Figure 5-1 FRBACKUP PREPARE elapsed
Page 256 and 257: Figure 5-4 BACKUP SYSTEM FULL measu
Page 258 and 259: 5.1.2 Conclusion The BACKUP SYSTEM
Page 260 and 261: Figure 5-7 shows the sliding scale
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
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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
Page 288 and 289: Note that when the qualified partit
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Page 292 and 293: 5.6.10 Support for more than 245 se
Page 294 and 295: 6.1 Online CHECK INDEX Online CHECK
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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 308 and 309: ► Number of column groups: 1 ►
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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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DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

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