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

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9.1 Unicode catalog DB2 for z/OS supports three types of encoding schemes: ► EBCDIC ► ASCII ► UNICODE Traditionally IBM mainframes have been based on EBCDIC, while Unix and Windows applications are based on ASCII. Beginning with Windows NT®, everything stored in Windows was stored in Unicode (UTF-16). To handle larger character sets, which are absolutely necessary in Asian languages, double byte characters and mixtures of single byte and double byte characters were necessary. Each national language developed its own code pages in EBCDIC or ASCII. The character set for a language is identified by a numeric CCSID. An encoding scheme consists of a single byte character set (SBCS), and optionally a double byte character set (DBCS) along with a mixed character set. For example, the EBCDIC CCSID used by the z/OS operating system itself is 37, but Japanese can use 8482 for SBCS, 16684 for DBCS and 1390 for mixed. Terminology: Translation is what we do going from language to another, while conversion is what we do to character strings. CCSIDs (and code pages) are never converted, they are just definitions. The individual character strings are converted. 9.1.1 Character conversion 9.1.2 Unicode parsing The variety of CCSIDs made it very difficult for multinational corporations to combine data from different sources. Unicode has arisen to solve the problem. By storing data in a single Unicode CCSID, text data from different languages in different countries can be easily managed. However, to make the transition to Unicode can be difficult and a lot of data conversion is unavoidable. When storing into and retrieving data from DB2, DB2 will convert data where necessary. Obviously, it is preferable that no conversion be carried out, because conversion impacts performance. However, considerable work has been done to improve conversion performance on zSeries. See 4.7, “Unicode” on page 174. Character conversion is necessary whenever there is a mismatch between the CCSID of a source and target string, such as between a host variable and its associated column. Such conversion support in DB2 has existed since DB2 began to support client/server connections. In DB2 V2.3 such translations started out between different EBCDIC CCSIDs, as well as between EBCDIC and ASCII. To perform such character conversion (not involving Unicode), DB2 uses a translate table which is stored in SYSIBM.SYSSTRINGS. We will refer to such conversions as SYSSTRINGS conversions, which have particular performance characteristics. In DB2 V8, because the catalog has changed to Unicode, data being sent or received by the application must be verified and possibly converted by the DBM1 address space. Figure 9-1 depicts a legacy COBOL application running in z/OS using CCSID 37. The database has been converted to Unicode. The table contains one CHAR column called COLC (CCSID 1208) and one GRAPHIC column called COLG (CCSID 1200). When the application inserts host variables HV1 and HV2 into the table, the strings are converted by the DBM1 address space into Unicode. The CPU time for these conversions is added to class 2 CPU time. 342 DB2 UDB for z/OS Version 8 Performance Topics
Figure 9-1 Unicode conversion example DB2 V8 brings significant enhancements in the Unicode area lifting restrictions that were in DB2 V7. These enhancements include Unicode parsing and the conversion of the DB2 Catalog to Unicode. DB2 V8 formalizes a two stage migration process that used to be followed by customers implicitly, but which is now enforced by DB2. When you first start DB2 V8, you are running in CM where the DB2 catalog is still in EBCDIC and you are prevented from exploiting new function. However, all SQL parsing in DB2 V8 is done in Unicode, that is, UTF-8, even in compatibility mode. SQL statements that are input in EBCDIC, ASCII or UTF-16 must be converted to UTF-8. In compatibility mode, metadata that is derived (in other words, parsed) from the SQL statement must be converted to EBCDIC in order to compare them to DB2 catalog data. When you migrate the catalog to new-function mode (NFM), the DB2 catalog is converted to Unicode, and fallback to V7 is no longer possible. New DB2 V8 installations always run in NFM. SQL statement conversion is unaffected by the switch to NFM, but metadata derived from SQL is no longer converted since the metadata is already in the CCSID of the DB2 catalog. On the other hand, Unicode conversion is introduced for column names specified within an SQLDA in EBCDIC or ASCII. DB2 V8 also introduces the capability to join two tables of different CCSIDs. Needless to say, Unicode conversion is necessary to do this and the extra CPU time is likely to be substantial. DB2 V8 major and minor conversion Conversion of SQL statements and metadata generally involves English alphanumeric characters. To improve performance, DB2 V8 developed a faster way to convert such characters without calling the z/OS Conversion Services. This fast method is called minor conversion, while major conversion refers to those conversions performed by the z/OS Conversion Services. DB2 does this by maintaining a translate table associated with the EBCDIC SBCS/single bytes of the mixed CCSIDs that are specified during DB2 installation. The same translate table is used for accesses to the DB2 catalog and user data. Minor conversion is supported for all European EBCDIC character sets, and some Asian EBCDIC character sets. Minor conversion does not apply to UTF-16 (GRAPHIC) or ASCII; it may only apply to conversions between EBCDIC and UTF-8. In a multinational corporate environment, we may see applications originating from different national languages accessing a common database. A Unicode database allows such a multinational corporation to store all of its data in a single database. Since we cannot assume Chapter 9. Installation and migration 343
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ibm.com/redbooks Front cover DB2 UD
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Note: Before using this information
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2.5.3 Increased number of deferred
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4.5.2 Conclusion . . . . . . . . .
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7.4.1 ODBC Unicode support . . . .
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x DB2 UDB for z/OS Version 8 Perfor
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3-48 Consistency query - 31 New . .
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xiv DB2 UDB for z/OS Version 8 Perf
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8-5 CF Request Batching - DB2 CPU .
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xviii DB2 UDB for z/OS Version 8 Pe
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Trademarks The following terms are
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Added information The following APA
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► Added reference to June 15, 200
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Michael Parbs is a DB2 Specialist w
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Hugh Smith Jim Teng John Tobler Yoi
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xxx DB2 UDB for z/OS Version 8 Perf
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1.1 Overview 1.1.1 Architecture IBM
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- Column data type changes can be d
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1.1.3 Data warehouse 1.1.4 Performa
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Volatile (or cluster) tables, used
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In this chapter we anticipate the a
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2.1.3 I/O time 2.1.4 Virtual storag
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► The performance benchmarks for
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application that can have great pot
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Because you can significantly incre
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The possible increase in thread foo
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2.5.9 Unicode parser Important: Con
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You can keep the DBRMs in EBCDIC fo
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Macro Parameter Old value New value
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28 DB2 UDB for z/OS Version 8 Perfo
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► Parallel sort enhancement Paral
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Characteristics of the host variabl
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3.1.4 Performance Update 10 rows us
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► Complexity of the fetch. The fi
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► More rows per one SQL statement
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3.2.1 Creating MQTs MQTs compared t
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Special register CURRENT REFRESH AG
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the materialized query table. If it
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Figure 3-9 MQTs and short running q
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► The elapsed time is 22 times sm
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Figure 3-13 Regrouping on MQT resul
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EVE.EXT = 'ADD BILL' AND EVE.TXC =
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Star Schema Figure 3-15 Star schema
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merge joins and work file usage. DB
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Star join access path without a spa
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3.3.4 Performance Sparse index for
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V8 Star Join Access Path Figure 3-2
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3.3.5 Conclusion Star join workload
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. SELECT * FROM PAOLO.TORDER WHERE
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But not all mismatched numeric type
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V8 shows that PL is joined with CV
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Query performance problem Lack of m
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3.5.1 Performance SORTDEVT SYSDA IN
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3.5.2 Conclusions Figure 3-31 Acces
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Mismatched data types SELECT COUNT(
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3.7.1 Performance In V8 the paralle
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3.7.2 Conclusions Example 3-9 Multi
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3.8.2 Performance We show three exa
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3.8.3 Conclusion The measurements s
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100 Inserts activated trigger 100 t
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3.10.2 Conclusion 100 Inserts activ
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stores the selected columns from ea
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While there is no optimistic lockin
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FETCH FROM Figure 3-45 FETCH syntax
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► Measurement data collected with
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application has decidedly higher Cl
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Static updatable cursor You can see
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Multi-row FETCH with a static curso
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3.12.5 Conclusion Multi-row FETCH a
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While, for or SELECT ... FROM ...
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3.14.2 Conclusion Percent reduction
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3.15.1 Installation commands. Of co
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Figure 3-47 Explain of the old cons
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in ms = 1 and the CPU cost is 16 se
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Figure 3-50 Suggested RUNSTATS stat
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Looking at the explanation, we can
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The Plug-In Options screen of Stati
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Before the introduction of MQTs, DB
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126 DB2 UDB for z/OS Version 8 Perf
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► Larger VSAM CI sizes: DB2 V8 in
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4.1.1 Performance support caused al
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Regression is about 5% better than
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The results indicate no significant
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Important: 4.1.2 Conclusion If you
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However, the combined impact of oth
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Frees up space below the bar for ot
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from the hiperpools, they were not
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So, we advise you to not overalloca
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See 4.3, “Monitoring DBM1 storage
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Table 4-4 System storage configurat
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Stack 11356 21033 85% 8648 19799 12
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KB 600 500 400 300 200 100 0 Figure
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For the same buffer pool size and o
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4.2.3 Conclusion Nondistributed per
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Important: With PTFs UK04394 (DB2 V
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- DATASPACE BP CONTROL BLOCKS = 0 M
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The EXTENDED REGION SIZE (MAX) is t
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RDS OP POOL (MB) N/A RID POOL (MB)
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As you can now appreciate, it is im
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Megabytes A V7 Customer DBM1 Thread
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4.5.1 Performance The most buffer p
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4.6.1 Performance maintained in a 2
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4.6.2 Conclusion We can conclude th
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service for Unicode conversions, an
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overcome this, when DB2 Connect is
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INSERT HV1 1200 HV2 1200 SELECT HV1
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AIX C-program Conversion Routines P
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4.7.1 Performance The improvements
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In October 2003, a new enhancement
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UseServerEncoding data source prope
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4.8.1 Performance 4.8.2 Conclusion
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Multilevel security with row-level
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► The security level that defines
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DB2 must call RACF for this dominan
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4.9.2 Conclusion The CPU increase c
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4.10.1 Performance VSAM does not kn
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4.10.2 Conclusion 4.10.3 Striping A
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5 4 3 2 1 0 9109TLLB 4 Parallel DB2
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This message is completed with the
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This enhancement is introduced by P
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This record is activated by: -START
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an online transaction with very sim
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5.1 System level point-in-time reco
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BACKUP SYSTEM During backup DB2 rec
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Figure 5-1 FRBACKUP PREPARE elapsed
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Figure 5-4 BACKUP SYSTEM FULL measu
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5.1.2 Conclusion The BACKUP SYSTEM
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Figure 5-7 shows the sliding scale
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Maybe you have implemented a space
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For dynamically prepared queries, D
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► CHAR(8) to VARCHAR(8) ► CHAR(
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Before ALTER INDEX add column, a ta
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30 25 20 15 10 Figure 5-12 FETCH CP
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Percent of index pages Avg. Index L
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300 250 200 time in seconds 150 100
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REORG REBALANCE We executed and mea
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5.4 Volatile table 5.4.1 Conclusion
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If explicit clustering for a table
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Load table of 20M rows, 10 partitio
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Times in seconds 20 18 16 14 12 10
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RUNSTATS INDEX PARTITION of a DPSI
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Note that when the qualified partit
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► “NO” - Values in such colum
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5.6.10 Support for more than 245 se
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6.1 Online CHECK INDEX Online CHECK
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SORTOUT DD UNIT=SYSDA,SPACE=(CYL,(5
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- SORT 6 indexes in parallel - CHEC
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make DB2 take the maximum paralleli
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6.3 LOAD and UNLOAD delimited input
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6.3.2 Conclusion We measured the CP
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Options for cardinality and distrib
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► Number of column groups: 1 ►
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cases is the total time of RUNSTATS
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6.4.5 Conclusion Statistics Advisor
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goals for end-user services. We sho
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alanced across all members. With th
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method. Prior to DB2 V8 those array
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when compared to DB2 V7. At the ser
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7.2.2 Performance - Distributed cli
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Page 326 and 327: ► The DB2 Universal JDBC type 4 D
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Page 336 and 337: The SYSIBM.INDOUBT table and the pa
Page 338 and 339: Batch updates A batched update is a
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Page 352 and 353: Impact on coupling facility: You do
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Page 366 and 367: Table 8-12 DB2 I/O CI Limit Removal
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Page 376 and 377: that all applications are converted
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Page 380 and 381: From these measurements we observe
Page 382 and 383: Class 1 CPU time (MSEC) 200 150 100
Page 384 and 385: dynamic statement cache. If activat
Page 386 and 387: that everything is ready. This step
Page 388 and 389: Table Number of rows SYSDATABASE 75
Page 390 and 391: In Figure 9-7 we describe the perfo
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Page 396 and 397: 10.1 DB2 Estimator DB2 Estimator V8
Page 398 and 399: - REAL AND AUXILIARY STORAGE This i
Page 400 and 401: Another use is during back out of a
Page 402 and 403: In DB2, the IBM Data Encryption too
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Page 410 and 411: A.1 Maintenance for DB2 V8 The APAR
Page 412 and 413: APAR # Area Text PTF and Notes PQ88
Page 416 and 417: APAR # Area Text PTF and Notes PK21
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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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