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

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7.3.2 <strong>DB2</strong> Universal Driver X/Open XA support<br />

One of the key reasons <strong>for</strong> using the Universal Driver in a type 2 architecture is <strong>for</strong> local<br />

application per<strong>for</strong>mance and <strong>for</strong> distributed transaction support (XA). XA support was first<br />

provided in the <strong>DB2</strong> Universal Type 2 Driver and became available in the Type 4 Driver with<br />

<strong>DB2</strong> V8.1 <strong>for</strong> Multiplat<strong>for</strong>ms FP4. MQSeries® classes <strong>for</strong> Java Message Service include the<br />

JMS XA interface. These allow MQ JMS to participate in a two-phase commit that is<br />

coordinated by a transaction manager that complies with the Java Transaction API (JTA).<br />

Description<br />

If the application will be involved in a distributed transaction, the<br />

COM.ibm.db2.jdbc.<strong>DB2</strong>XADataSource class should be used when defining <strong>DB2</strong> data<br />

sources within the WebSphere Application Server.<br />

Per<strong>for</strong>mance<br />

The internal throughput was measured <strong>for</strong> a servlet workload using the Type 2 non-XA versus<br />

the Type 2 XA compliant driver. The environment used in this measurement was z/<strong>OS</strong> V1.3,<br />

<strong>DB2</strong> <strong>for</strong> z/<strong>OS</strong> V8 and WAS V5.0.2. See Figure 7-17.<br />

WebSphere z/<strong>OS</strong> - <strong>DB2</strong> <strong>for</strong> z/<strong>OS</strong> V8 - Servlet workload ...<br />

JCC type 2 - non-XA vs. XA<br />

WebSphere<br />

V502<br />

servlet<br />

z/<strong>OS</strong> 1.3<br />

JCC<br />

T2<br />

1.8.36<br />

<strong>DB2</strong><br />

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

V8<br />

Figure 7-17 Servlet workload - Type 2 non-XA vs. Type 2 XA compliant driver<br />

200<br />

150<br />

100<br />

50<br />

0<br />

non-XA driver<br />

The results are less than 1% of internal throughput ratio (ITR= Units of Work/Processor Busy)<br />

reduction when using the type 2 XA compliant driver. This means that there is practically no<br />

extra overhead in choosing the driver with distributed transaction support from WebSphere.<br />

<strong>DB2</strong> client application programs that run under the <strong>DB2</strong> Universal JDBC Driver can use<br />

distributed transaction support in <strong>DB2</strong> V7 and <strong>DB2</strong> V8. <strong>DB2</strong> V8 servers include native XA<br />

mode support. However, <strong>DB2</strong> V7 servers do not have native XA mode support, so the <strong>DB2</strong><br />

Universal JDBC Driver emulates the XA mode support using the existing <strong>DB2</strong> DRDA<br />

two-phase commit protocol. This XA mode emulation uses a <strong>DB2</strong> table named<br />

SYS<strong>IBM</strong>.INDOUBT to store in<strong>for</strong>mation about indoubt transactions. <strong>DB2</strong> uses a package<br />

named T4XAIndbtPkg to per<strong>for</strong>m SQL operations on SYS<strong>IBM</strong>.INDOUBT.<br />

XA driver<br />

Normalized transactions<br />

per second<br />

Chapter 7. Networking and e-business 303

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