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

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AIX C-program Conversion Routines Prepare 943 Prepare 943 DB2 UDB client code V8 DRDA Common Layer Figure 4-17 CCSID conversion - Remote Prepare of SQL statement The application on AIX typically inputs the SQL statement in ASCII, whether the target DB2 server is V7 or V8. So, DB2 V7 converts the statement from ASCII to EBCDIC, and DB2 V8 converts the SQL statement from ASCII to UTF-8. Finally, Figure 4-18 shows a local prepare of an SQL statement using the Universal Java Type 2 Driver to connect to DB2 V7 and DB2 V8. Java Application Prepare 1200 Prepare 1200 USS Universal Java T2 Driver 1208 1208 Figure 4-18 CCSID conversion - Local Prepare using Universal Java Type 2 Driver The Legacy JDBC Driver converts the SQL statement from UTF-16 to UTF-8, which requires no conversion on DB2 V8. 182 DB2 UDB for z/OS Version 8 Performance Topics DB2 V7 on z/OS DDF DBM1 DB2 V8 on z/OS DDF DBM1 z/OS RRS DB2 V7 DBM1 DB2 V8 DBM1 1390 1208 1390 1208 DB2 V7 Catalog DB2 V8 Catalog DB2 V7 Catalog DB2 V8 Catalog
Choosing between UTF-8 and UTF-16 When choosing to store data in a Unicode database, you have a choice of using either UTF-8 (CHAR) or UTF-16 (GRAPHIC). This choice includes both performance and non-performance considerations. For example, since the collating sequences of UTF-8 and UTF-16 are different, you can choose column types based on the desired collating sequence rather than performance. However, the major performance consideration when comparing UTF-8 to UTF-16 is the amount of space used. The reason space is important is not just the cost of the space itself, but also the impact that the space has on I/O bound utilities and queries, including the time to recover, which affects data availability. Buffer pool hit ratios are also affected by space. A UTF-8 character is variable length and can be 1 to 4 bytes in length, of which the first 128 code points match 7-bit ASCII. A UTF-8 character is used by DB2 to store CHAR or VARCHAR columns. This is opposed to a character in UTF-16, which is 2 or 4 bytes. DB2 uses UTF-16 to store GRAPHIC or VARGRAPHIC columns. The first 128 code points match UTF-8 and ASCII, while the rest have a different collating sequence. Consider the type of data you will be storing in DB2 and choose UTF-8 (CHAR) or UTF-16 (GRAPHIC), depending on the characteristics of the data. UTF-8 is efficient for text that is predominantly English alphanumeric while UTF-16 is more efficient for Asian characters. To reduce the space required by Unicode tables, you can use DB2 compression. With no DB2 compression and for alphanumeric characters, UTF-8 has the same space characteristics as EBCDIC, however UTF-16 doubles the storage requirements. Compressed alphanumeric UTF-16 strings use more storage than compressed alphanumeric UTF-8 strings, but the ratio is generally much less than 2 to 1. Tests have shown this ratio can be less than 1.5 to 1. Whether compression is used or not, the overall effect of Unicode on space usage depends on the amount of text data versus non-text data. CPU time can also be another consideration. Compression itself costs a lot of CPU time, although its I/O benefits can outweigh the CPU costs. In some applications Unicode conversion can be avoided, but if conversion must be done, it is best done by a remote client in order to distribute the CPU overhead. If conversion must be done on the zSeries machine, then you should consider what the dominant application CCSID will be. Generally, the choice which tends to minimize space usage also tends to minimize CPU usage. Choosing between fixed and variable length strings may also be another consideration. Remember, the length of a UTF-8 string is unpredictable, unless the application limits the characters to the common set and fixed length strings. Consider, for example, a column that was defined as CHAR(1) in EBCDIC. If you try to insert a multibyte UTF-8 character into CHAR(1), you get a -302 SQL error, because the data does not fit into one byte. If you change the column definition to GRAPHIC(1), you need two bytes. If you change the column definition to VARCHAR, you need 3 bytes in order to account for the two-byte length field. Knowing that a field is restricted to alphanumeric characteristics allows you to continue using CHAR(1). It is especially good to avoid using variable length fields in indexes, especially nonpadded indexes, since key comparisons of variable length fields are more expensive. On the other hand, you should try to avoid padding costs with fixed length fields if Unicode conversion is being done. Remember, there is nothing stopping you from storing both UTF-8 and UTF-16 encoded data in the same table. Chapter 4. DB2 subsystem performance 183
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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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Page 166 and 167: The results indicate no significant
Page 168 and 169: Important: 4.1.2 Conclusion If you
Page 170 and 171: However, the combined impact of oth
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Page 174 and 175: from the hiperpools, they were not
Page 176 and 177: So, we advise you to not overalloca
Page 178 and 179: See 4.3, “Monitoring DBM1 storage
Page 180 and 181: Table 4-4 System storage configurat
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Page 184 and 185: KB 600 500 400 300 200 100 0 Figure
Page 186 and 187: For the same buffer pool size and o
Page 188 and 189: 4.2.3 Conclusion Nondistributed per
Page 190 and 191: Important: With PTFs UK04394 (DB2 V
Page 192 and 193: - DATASPACE BP CONTROL BLOCKS = 0 M
Page 194 and 195: The EXTENDED REGION SIZE (MAX) is t
Page 196 and 197: RDS OP POOL (MB) N/A RID POOL (MB)
Page 198 and 199: As you can now appreciate, it is im
Page 200 and 201: Megabytes A V7 Customer DBM1 Thread
Page 202 and 203: 4.5.1 Performance The most buffer p
Page 204 and 205: 4.6.1 Performance maintained in a 2
Page 206 and 207: 4.6.2 Conclusion We can conclude th
Page 208 and 209: service for Unicode conversions, an
Page 210 and 211: overcome this, when DB2 Connect is
Page 212 and 213: INSERT HV1 1200 HV2 1200 SELECT HV1
Page 216 and 217: 4.7.1 Performance The improvements
Page 218 and 219: In October 2003, a new enhancement
Page 220 and 221: UseServerEncoding data source prope
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
Page 242 and 243: This enhancement is introduced by P
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Page 246 and 247: an online transaction with very sim
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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
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For dynamically prepared queries, D
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► CHAR(8) to VARCHAR(8) ► CHAR(
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Before ALTER INDEX add column, a ta
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30 25 20 15 10 Figure 5-12 FETCH CP
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Percent of index pages Avg. Index L
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300 250 200 time in seconds 150 100
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REORG REBALANCE We executed and mea
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5.4 Volatile table 5.4.1 Conclusion
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If explicit clustering for a table
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Load table of 20M rows, 10 partitio
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Times in seconds 20 18 16 14 12 10
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RUNSTATS INDEX PARTITION of a DPSI
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Note that when the qualified partit
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► “NO” - Values in such colum
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5.6.10 Support for more than 245 se
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6.1 Online CHECK INDEX Online CHECK
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SORTOUT DD UNIT=SYSDA,SPACE=(CYL,(5
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- SORT 6 indexes in parallel - CHEC
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make DB2 take the maximum paralleli
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6.3 LOAD and UNLOAD delimited input
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6.3.2 Conclusion We measured the CP
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Options for cardinality and distrib
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► Number of column groups: 1 ►
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cases is the total time of RUNSTATS
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6.4.5 Conclusion Statistics Advisor
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goals for end-user services. We sho
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alanced across all members. With th
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method. Prior to DB2 V8 those array
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when compared to DB2 V7. At the ser
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7.2.2 Performance - Distributed cli
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Recommendation If you currently do
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► The DB2 Universal JDBC type 4 D
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WebSphere z/OS - DB2 z/OS V8 - Serv
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DB2 Universal Type 4 Driver - JDBC
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Use DB2 Connect when a high amount
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JCC Type 4 Direct 4:3 Concentration
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The SYSIBM.INDOUBT table and the pa
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Batch updates A batched update is a
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Example In DB2 V8 SQL/XML publishin
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INSERT INTO PUB_TAB(DOC) SELECT XML
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7.5.3 Conclusion The new XML publis
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A second role of the managed server
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7.6.3 Performance The following inf
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Impact on coupling facility: You do
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Table 8-1 shows extracts from DB2 P
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and secondary GBP structures have t
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DB2 member already has the table sp
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8.2.1 Performance We ran a number o
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esolve any contention. This extra a
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There is also no need to use RELEAS
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Table 8-12 DB2 I/O CI Limit Removal
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8.5 Miscellaneous items In this sec
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DB2 V8 improves Restart Light. If i
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9.1 Unicode catalog DB2 for z/OS su
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that all applications are converted
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- CLASST: Specifies the threshold a
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From these measurements we observe
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Class 1 CPU time (MSEC) 200 150 100
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dynamic statement cache. If activat
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that everything is ready. This step
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Table Number of rows SYSDATABASE 75
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In Figure 9-7 we describe the perfo
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Old - Query 5 New - Query 5 CPU (se
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Query 35 36 Old DSNTESQ CPU 1 hr 1
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10.1 DB2 Estimator DB2 Estimator V8
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- REAL AND AUXILIARY STORAGE This i
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Another use is during back out of a
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In DB2, the IBM Data Encryption too
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The utilities ran on a G7 Turbo wit
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time Figure 10-1 DB2 HPU vs. UNLOAD
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DSNTIAUL with multi-row fetch The r
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A.1 Maintenance for DB2 V8 The APAR
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APAR # Area Text PTF and Notes PQ88
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APAR # Area Text PTF and Notes PK21
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B.1 DB2 PE Storage Statistics trace
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Storage heading Description 24 BIT
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C.1 DB2 SQL PA additional reports N
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|is the last matching predicate. Ap
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|ANL6052I *** NOTE: | |This index i
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PREDICATE ANALYSIS ----------------
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D.1 DB2 EXPLAIN EXPLAIN describes t
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Table D-2 PLAN_TABLE contents and b
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Column Type Content SORTC_ORDER BY
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Column Type Content OPTHINT CHAR(8)
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D.1.3 DSN_FUNCTION_TABLE You can us
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Example: D-1 Creating DSN_STATEMENT
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Column Type Content BIND_QUALIFIER
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ICF integrated catalog facility ICF
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► DB2 UDB for z/OS V8: Through th
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character set 174 CHECK DATA 262 CH
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Equi-join predicates 54, 402 Equiva
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MINSTOR 145-146 Mismatched data typ
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PQ84160 378, 387 PQ85764 387 PQ8584
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Sort tree nodes 144 SORTDATA 268 SO
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306 Universal Driver for SQLJ and J
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DB2 UDB for z/OS Version 8 Performa
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