as400 developer Interview Questions and Answers

1. What is AS400 (now IBM i)?

   • Answer: IBM i (formerly known as AS/400) is a family of robust, enterprise-class servers designed for mission-critical business applications. It's known for its reliability, security, and integrated database system (DB2 for i). It uses a unique architecture that integrates the operating system, database, and programming languages into a single, tightly coupled system.

2. Explain the concept of integrated database in IBM i.

   • Answer: The integrated database in IBM i means that the database is not a separate entity but is intrinsically part of the operating system. Data is stored as integrated database files, directly accessible by the operating system and applications without the need for separate database drivers or connections. This results in improved performance and simplified data management.

3. What are the main programming languages used for IBM i development?

   • Answer: RPG (Report Program Generator), COBOL, CL (Control Language), and Java are the primary languages. Modern development also utilizes PHP, Python, Node.js and others through integrations.

4. What is RPG and its different versions?

   • Answer: RPG is a high-level programming language originally designed for report generation. It has evolved significantly over the years. Key versions include RPG II, RPG III, RPG IV (now often just called RPG), and modern RPG which incorporates free-form coding styles and enhanced capabilities.

5. Explain the differences between RPG III and RPG IV/Free.

   • Answer: RPG III uses a fixed-format source code with strict columnar definitions for different code elements. RPG IV/Free allows for free-form coding, making it more readable and easier to maintain. RPG IV/Free also provides enhanced features like subroutines, procedures, and more modern programming constructs.

6. What is CL (Control Language)? What is it used for?

   • Answer: CL is a command-line language used to control the IBM i system. It's used for tasks such as job scheduling, system administration, program execution, and interacting with system objects. It provides a powerful way to automate system tasks.

7. What is DB2 for i? How does it differ from other relational databases?

   • Answer: DB2 for i is the integrated relational database management system (RDBMS) for IBM i. It's tightly coupled with the operating system, offering advantages in performance and data integrity. Key differences from other RDBMS include its integrated nature, the use of database files as operating system files, and its strong support for data access from different programming languages.

8. How do you handle errors in RPG programs?

   • Answer: Error handling in RPG typically involves using exception handling mechanisms (e.g., MONITOR groups), checking return codes from subroutines, and using indicators to flag conditions. Detailed error messages can be logged and displayed to the user.

9. Explain the concept of Data Areas in IBM i.

   • Answer: Data areas are simple database-like objects used to store relatively small amounts of data that can be accessed by multiple programs. They are useful for things like storing configuration settings, system status information, or temporary variables shared among programs.

10. What are Service Programs in IBM i?

    • Answer: Service programs are collections of modules (procedures or subroutines) that can be called from multiple programs. They promote modularity and code reusability, making programs easier to maintain and reducing redundancy.

11. Describe your experience with SQL in the context of IBM i.

    • Answer: [This requires a personalized answer based on the candidate's experience. The answer should describe their proficiency in using SQL to query and manipulate data in DB2 for i, including experience with different SQL statements (SELECT, INSERT, UPDATE, DELETE), joins, subqueries, and stored procedures.]

12. How do you debug RPG programs? What tools do you use?

    • Answer: Debugging RPG programs involves using tools like the IBM i debug tool (STRDBG), which allows for stepping through the code, inspecting variables, and setting breakpoints. Modern IDEs like Rational Developer for i also provide advanced debugging features.

13. What is the role of spooling files in IBM i?

    • Answer: Spooling files are temporary storage areas for output generated by programs, such as reports or printed documents. They allow programs to continue execution while the output is processed or printed, improving performance.

14. Explain the concept of output queues in IBM i.

    • Answer: Output queues are used to manage and route spooled files to printers, other devices, or users. They provide control over the order of processing, priority, and the destination of output.

15. How do you handle data conversions in IBM i?

    • Answer: Data conversions in IBM i involve techniques like using built-in functions (e.g., %CHAR, %DEC, %DATE) within RPG or using external tools or utilities to convert data formats between different systems.

16. What are some common performance tuning techniques for IBM i applications?

    • Answer: Performance tuning techniques include optimizing SQL queries, using appropriate data types, indexing database files, creating efficient service programs, minimizing disk I/O, and using appropriate memory allocation.

17. What are your experiences with IBM i security?

    • Answer: [This requires a personalized answer based on the candidate's experience. The answer should include discussion of user profiles, authorities, object security, and encryption techniques used in IBM i.]

18. How do you manage source code in IBM i development?

    • Answer: Source code management typically involves using source code control systems, such as Git, although older methods like using libraries and source physical files on the IBM i itself might be used. Version control is crucial for collaborative development and tracking changes.

19. Explain your experience with Integrated File System (IFS) on IBM i.

    • Answer: [This requires a personalized answer based on the candidate's experience. The answer should discuss their use of the IFS for storing and accessing various types of files using a hierarchical file system, similar to Unix or Windows.]

20. What is your experience with web services and APIs on IBM i?

    • Answer: [This requires a personalized answer based on the candidate's experience. The answer should describe experience with technologies such as REST APIs, SOAP web services, and any relevant frameworks used for creating and consuming web services on the IBM i platform.]

21. How familiar are you with different types of data structures in RPG?

    • Answer: [This requires a personalized answer, but should include discussion of arrays, data structures, pointers, and how they are used in RPG programs.]

22. Describe your experience with modernizing legacy IBM i applications.

    • Answer: [This requires a personalized answer. The answer should discuss strategies like refactoring code, upgrading to modern RPG versions, integrating with new technologies, and modernizing the user interface.]

23. How do you approach performance optimization in a database-intensive IBM i application?

    • Answer: This involves analyzing SQL queries using query optimization tools, adding indexes where necessary, optimizing data access patterns, and potentially re-designing database tables or views to improve performance.

24. Explain your understanding of database triggers in DB2 for i.

    • Answer: Database triggers are stored procedures that automatically execute in response to certain events on a table or view, such as INSERT, UPDATE, or DELETE operations. They can be used to enforce data integrity, implement business rules, and automate tasks.

25. What are your experiences with using external libraries or APIs in IBM i programming?

    • Answer: [This requires a personalized answer. The answer should discuss how the candidate has integrated with external systems or services via APIs or libraries.]

26. How do you handle concurrency in IBM i applications?

    • Answer: Concurrency is handled through techniques like proper locking mechanisms within DB2 for i, using appropriate isolation levels, and carefully managing access to shared resources to prevent data corruption or inconsistencies.

27. Describe your experience with using version control systems for IBM i development.

    • Answer: [This requires a personalized answer. It should demonstrate understanding of using tools like Git or other version control systems to manage source code, track changes, and collaborate effectively.]

28. What are some best practices for writing maintainable and readable RPG code?

    • Answer: Best practices include using meaningful variable names, adding comments, following consistent indentation, modularizing code into reusable subroutines, and adhering to coding standards.

29. Explain your understanding of different types of joins in SQL.

    • Answer: This includes INNER JOIN, LEFT JOIN (OUTER JOIN), RIGHT JOIN (OUTER JOIN), and FULL OUTER JOIN. The answer should describe how each join type works and when it is appropriate to use them.

30. How do you ensure data integrity in IBM i applications?

    • Answer: Data integrity is ensured through techniques like using constraints (e.g., NOT NULL, UNIQUE, CHECK) in DB2 for i, employing triggers to enforce business rules, and properly validating data input and output.

31. What are your experiences with automated testing in IBM i development?

    • Answer: [This requires a personalized answer. The answer should discuss the use of unit testing, integration testing, or other automated testing frameworks.]

32. How do you handle large datasets in IBM i applications?

    • Answer: Handling large datasets requires efficient querying techniques, using appropriate indexes, potentially partitioning tables, and optimizing data access patterns. Techniques like paging or batch processing might be necessary.

33. What are your experiences with working in a team environment on IBM i projects?

    • Answer: [This requires a personalized answer, demonstrating teamwork skills and collaborative experience.]

34. Describe your problem-solving approach when dealing with complex issues in IBM i applications.

    • Answer: [This requires a personalized answer, showing a systematic approach to troubleshooting, including using debugging tools, analyzing logs, and seeking help from colleagues or resources.]

35. How do you stay up-to-date with the latest technologies and trends related to IBM i development?

    • Answer: [This requires a personalized answer, showing a commitment to continuous learning, mentioning resources like IBM's website, developer communities, conferences, or training courses.]

36. What are your salary expectations?

    • Answer: [This requires a personalized answer, based on research and experience.]

37. Why are you interested in this position?

    • Answer: [This requires a personalized answer, demonstrating genuine interest in the company and the role.]

38. What are your strengths and weaknesses?

    • Answer: [This requires a personalized answer, highlighting relevant skills and honestly addressing areas for improvement.]

39. Tell me about a time you had to work under pressure.

    • Answer: [This requires a personalized answer, showcasing problem-solving skills and ability to handle stress.]

40. Tell me about a time you failed. What did you learn from it?

    • Answer: [This requires a personalized answer, demonstrating self-awareness and learning from mistakes.]

41. Describe your experience with different database design methodologies.

    • Answer: [This requires a personalized answer, discussing experience with normalization, database modeling techniques, and understanding of relational database design principles.]

42. What is your experience with performance monitoring and optimization tools for IBM i?

    • Answer: [This requires a personalized answer, mentioning specific tools and techniques used for performance analysis and optimization on IBM i systems.]

43. How do you handle version conflicts when working with source code control?

    • Answer: This usually involves resolving conflicts through careful comparison and merging of changes. The answer should demonstrate understanding of conflict resolution processes within the chosen version control system.

44. What is your understanding of the IBM i system architecture?

    • Answer: The answer should demonstrate understanding of the integrated nature of the OS, database, and middleware, as well as the unique aspects of the IBM i architecture such as its virtual storage and object-based system.

45. Describe your experience with using and managing IBM i libraries.

    • Answer: This should cover topics such as library lists, object creation, object management, and library dependencies.

46. What are some common security vulnerabilities in IBM i systems and how can they be mitigated?

    • Answer: The answer should discuss security issues like weak passwords, unauthorized access, and insecure configurations, and suggest mitigation techniques like strong passwords, access control lists, and regular security audits.

47. Explain your understanding of the IBM i job scheduler.

    • Answer: The answer should demonstrate knowledge of job scheduling functionality, including creating and managing jobs, setting schedules, and managing job queues.

48. How familiar are you with the concept of high availability and disaster recovery for IBM i?

    • Answer: The answer should cover techniques such as clustering, mirroring, backups, and failover mechanisms to ensure high availability and business continuity.

49. What are your experiences with using and managing IBM i network services?

    • Answer: This should cover areas like TCP/IP configuration, DNS, network security, and other network-related tasks.

50. How familiar are you with IBM i's support for different character sets and code pages?

    • Answer: The answer should cover the different character sets and code pages available on IBM i and how to manage them within applications.

51. What are your experiences with database backup and recovery procedures on IBM i?

    • Answer: This should discuss the different backup methods, recovery techniques, and the importance of regular backups and testing.

52. Explain your understanding of IBM i's support for different file types (e.g., physical files, logical files, etc.).

    • Answer: This should demonstrate a strong understanding of the different file types available on IBM i and their use cases.

53. Describe your experience with using IBM i's command-line interface (CLI).

    • Answer: This should demonstrate the candidate's familiarity with navigating the system, executing commands, and using the CLI for system administration tasks.

54. How familiar are you with using and managing IBM i's user profiles and authorities?

    • Answer: This should demonstrate knowledge of user profile creation, authority management, and security best practices.

55. What is your experience with working with external interfaces (e.g., APIs, web services) to integrate IBM i systems with other systems?

    • Answer: This should showcase experience with various integration methods and technologies.

56. Describe your experience with using and configuring IBM i's output queues.

    • Answer: This should demonstrate knowledge of creating, managing, and configuring output queues for different output devices and purposes.

57. What is your experience with using IBM i's spooling system?

    • Answer: This should cover the use of spooled files, managing spooled file attributes, and troubleshooting spooling issues.

58. What are your experiences with using different IBM i development tools (e.g., debuggers, IDEs)?

    • Answer: This should list specific tools used and demonstrate proficiency in using them.

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