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

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INSERT<br />

HV1 1200<br />

HV2 1200<br />

SELECT<br />

HV1 1200<br />

HV2 1200<br />

Java program<br />

INSERT<br />

HV1 1200<br />

HV2 1200<br />

SELECT<br />

HV1 1200<br />

HV2 1200<br />

JVM<br />

JVM<br />

Java Universal T2 Driver<br />

z/<strong>OS</strong><br />

z/<strong>OS</strong><br />

RRSAF<br />

RRSAF<br />

Figure 4-15 CCSID conversion - Local z/<strong>OS</strong> Universal Java Type 2 Driver<br />

Here we see that <strong>DB2</strong> <strong>for</strong> z/<strong>OS</strong> never has to do any CCSID conversion because the Universal<br />

Java Driver always converts the data to the correct CCSID. Hence, Unicode conversion does<br />

not affect class 2 CPU time, but since the JVM (Java Virtual Machine) is running on z/<strong>OS</strong>,<br />

conversions per<strong>for</strong>med under the JVM affect the class 1 CPU time. Note also that when a<br />

string is being inserted into or fetched from a Graphic Unicode column, there are no<br />

conversions under the JVM.<br />

As an aside, the Unicode conversions per<strong>for</strong>med by the JVM in z/<strong>OS</strong> do not use the z/<strong>OS</strong><br />

Conversion Services because it is difficult <strong>for</strong> the JVM to use z/<strong>OS</strong> system services. Prior to<br />

JDK Release 1.4.1 the conversions within Java did not use any of the special zSeries<br />

translation instructions, and the conversions were inefficient <strong>for</strong> long strings. Starting with<br />

JDK 1.4.1, some of these conversions are beginning to use the zSeries translate instructions,<br />

namely the TROO, TROT and TRTO instructions, which are useful <strong>for</strong> converting among byte<br />

codes and UTF-16 and SBCS EBCDIC characters. So, we can see improved per<strong>for</strong>mance <strong>for</strong><br />

the Universal Type 2 Driver, with particularly significant improvements with large SBCS<br />

strings on the z990 processor. Such an improvement does not occur when a string contains<br />

DBCS characters.<br />

180 <strong>DB2</strong> <strong>UDB</strong> <strong>for</strong> z/<strong>OS</strong> <strong>Version</strong> 8 Per<strong>for</strong>mance <strong>Topics</strong><br />

<strong>DB2</strong> <strong>for</strong> z/<strong>OS</strong><br />

Java program Java Universal T2 Driver<br />

DBM1<br />

<strong>DB2</strong> <strong>for</strong> z/<strong>OS</strong><br />

DBM1<br />

1390 COLC<br />

16684 COLG<br />

1390 COLC<br />

16684 COLG<br />

1208 COLC<br />

1200 COLG<br />

1208 COLC<br />

1200 COLG

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