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Java Stored Procedures in DB2 for OS/390

Java Stored Procedures in DB2 for OS/390. O pen, P ortable A pplication L ogic. Julian Stuhler DB2/CICS/IMS GUIDE May 2000. Topics. Introduction Java Stored Procedures – An Overview Environment Set-up Developing & Testing JSPs Usage Considerations Summary. Introduction.

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Java Stored Procedures in DB2 for OS/390

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  1. Java Stored Procedures in DB2 for OS/390 Open, Portable Application Logic Julian Stuhler DB2/CICS/IMS GUIDE May 2000

  2. Topics • Introduction • Java Stored Procedures – An Overview • Environment Set-up • Developing & Testing JSPs • Usage Considerations • Summary

  3. Introduction

  4. Introduction • DB2 consultant with Triton Consulting, based in the UK • 14 years DB2 experience • Database Administration • Systems Programming • Application Development • IBM Gold Consultant • Redbook – DB2 Network Computing Enhancements & Java Stored Procedures

  5. JSPs – An Overview

  6. What’s a Stored Procedure? • A program or routine executed by the database server in response to an SQL CALL statement issued by a client • Can receive and return parameters from / to calling client • Can enhance performance by replacing multiple SQL client calls • Can promote code re-use and consistency • Can improve security

  7. Supported Languages • Can be written in a wide variety of languages • Cobol • C/C++ • Assembler • PL/1 • REXX* • PSM* • Java* * Needs additional APAR support for V5 and V6

  8. Java Stored Procedures • Prerequisites • OS/390 Unix System Services (USS) • OS/390 Recoverable Resource Services (RRS) and Workload Manager (WLM) • DB2 For OS/390 V5 or V6 (with necessary additional APARs) • Enterprise Toolkit for OS/390 (part of VisualAge for Java) • Features • Open and fully portable code • High Performance Java support • JDBC (dynamic) and SQLJ (static) support

  9. High Performance Java • HPJ compiler (part of ET/390) compiles Java into standard OS/390 machine code • Advantages • Very high performance • Retain code portability • Allows WLM-managed stored procedures address space to run Java SPs without JVM support • Disadvantages • More complex program preparation process

  10. Java Terminology • Class • Equivalent to a module in traditional programming • Method • Equivalent to an entry point in traditional programming • Package • A collection of related Java classes, “packaged” as a single unit • Not to be confused with a DB2 package!

  11. Environment Overview OS/390 Load Library DBRM Library USS Source Code Links WLM Serialised Profiles Executing SP

  12. Runtime Environment

  13. Environment Set-Up

  14. Environment Set-Up • Complex environment • Plenty of pre-requisites • OS/390 • DB2 • Allow plenty of time to install all pre-requisites and get sample applications working • Good communications needed between DB2 and USS systems support staff

  15. Set-Up Tasks - 1 • Design library naming standards • USS • High Performance Java (HPJ) libraries • SQLJ/JDBC libraries • Links directory • Serialised profiles directory • OS/390 • HPJ SQLJ load library • Application stored procedure load library • JAVAENV dataset • DBRM library

  16. Set-Up Tasks - 2 • Create .profile script • Probably subsystem-specific • Set up new WLM environment for JSPs • Needs RRS enabled • Create HPJ versions of JDBC/SQLJ drivers • Create JAVAENV dataset • Tailor SQLJ properties and cursor files, if necessary

  17. Developing & Testing

  18. Coding • Most standard Java constructs can be used • Special code needed for null handling • E.g. to pass null input parameter from JDBC client to a stored procedure • Specific code to handle SQLJ iterators and result sets • Refer to SC26-9018, Application Programming Guide and Reference for Java

  19. Program Prep - JDBC

  20. Program Prep - SQLJ

  21. Error Handling & Debugging • Include provision for passing back results from SP in return parameters • Consider passing back meaningful message if problem encountered ( e.printStackTrace() ) • As for other types of stored procedures, debugging can be a problem • Output of Java println commands routed to JSPDEBUG in WLM SP JCL • Stored Procedure Builder and ET/390 Debugger tool provide additional facilities

  22. Usage Guidelines

  23. Naming Issues • Source files • One stored procedure (Java application class) per source file • Source file named after DB2 SP name • Java package name • One to one relationship with HPJ load module • Use same name for PDS/E member name • Group all related source files in single USS directory named after package • Many others to be considered • Java class name, Java method, DB2 packages, JAR files, etc

  24. DB2 Collections • Each SQLJ SP has 4 packages associated with it (one for each isolation level) • Collection containing these SPs must appear in package list for client issuing SP CALL • Use one collection for each Java package, with same name as the package • For JDBC, collection named in client’s package list must contain 4 generic JDBC packages • Collection name must match Java package name

  25. Case Sensitivity • Use upper case only for Java package names on S/390 • Ditto for other environments if portability is important • JDBC or SQLJ Java client calling a stored procedure must code SP name in upper case • SQLJ stored procedure must refer to DB2 object names in upper case (else –204)

  26. Packaging • Carefully consider number of SPs to group in a single Java package • Large number will result in large HPJ load module for the package, which may need excessive WLM storage • Small number will result in many DB2 collections to manage • Rules of thumb • Group together small, frequently used SPs • Keep larger SPs in their own Java package • Package remainder along application lines

  27. Portability • No code changes necessary to port JSP source files from one platform to another (e.g. Windows NT to OS/390) • Some changes may be required when porting client code • Class.forName (name of driver to be loaded) • Connection URL • Beware issues with ASCII/EBCDIC translation of Java curly brackets ({})

  28. Performance • Significant overhead on first use of a given module • Consider pre-staging critical modules and keeping them in storage • Once in storage, performance on a par with other methods • Use different WLM application groups to correctly prioritise workload

  29. Summary

  30. Summary • JSPs for DB2 for OS/390 provide an open, scaleable, high-performance way of encoding an application’s business logic • Tread carefully in the short term; • Complex environment set-up • New application development skills • DB2 code base still maturing

  31. Questions?

  32. For more information… Triton Consulting The Royal 25 Bank Plain Norwich NR2 4SF United Kingdom email:julian.stuhler@triton.co.uk http://www.triton.co.uk Tel: +44 (0) 870 2411550 Fax: +44 (0) 870 2411549

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