as400 programmer Interview Questions and Answers

1. What is the difference between CL and RPG programming languages in the AS400 environment?

   • Answer: CL (Control Language) is primarily used for system control, job scheduling, and managing AS400 resources. It's command-oriented. RPG (Report Program Generator) is a procedural language used for creating business applications, handling data manipulation, and generating reports. RPG is more powerful for complex data processing.

2. Explain the concept of DDS (Data Description Specifications) in AS400.

   • Answer: DDS is a language used to define the structure and characteristics of database files in AS400. It specifies field names, data types, lengths, and other attributes. DDS is crucial for creating and managing database files, defining display files for user interfaces, and controlling print files for reports.

3. Describe different types of files in AS400.

   • Answer: AS400 files include physical files (PFs) which store data, logical files (LFs) which provide customized views of data from PFs, and display files (DFs) used for user interaction. There are also other types like join files and member files.

4. What are subfiles in AS400 and how are they used?

   • Answer: Subfiles are used in display files to present multiple records on a single screen, allowing for efficient data entry and display of large datasets. They often involve scrolling and manipulation of multiple rows of data.

5. How do you handle errors and exceptions in RPG programs?

   • Answer: Error handling in RPG involves using MONITOR groups to trap exceptions, using indicators to check for errors, and employing exception handling routines to process and recover from errors gracefully.

6. Explain the concept of Data Queues in AS400.

   • Answer: Data queues are used for asynchronous communication between programs. One program writes messages to a data queue, and another program reads and processes them. This enables communication without direct coupling between programs.

7. What are the different types of joins you can perform in SQL on AS400?

   • Answer: Standard SQL joins are supported, including INNER JOIN, LEFT (OUTER) JOIN, RIGHT (OUTER) JOIN, and FULL (OUTER) JOIN. These allow for combining data from multiple tables based on related fields.

8. How do you use embedded SQL in RPG programs?

   • Answer: Embedded SQL allows you to write SQL statements directly within RPG programs. This combines the procedural capabilities of RPG with the data access power of SQL. Special keywords and precompiler steps are required.

9. What are some common performance tuning techniques for AS400 programs?

   • Answer: Performance tuning includes optimizing SQL queries, using appropriate indexes, minimizing I/O operations, using efficient data structures, and avoiding unnecessary calculations within loops.

10. Explain the significance of the WRKSPLF command.

    • Answer: WRKSPLF (Work with Spooled Files) is a powerful command used to manage and view spooled output files (like reports) generated by AS400 programs. It allows users to view, print, delete, and manage these files.

11. What is the purpose of the DSPPGM command?

    • Answer: DSPPGM (Display Program) is a CL command used to display information about a program, such as its source file, creation date, and other attributes.

12. How do you handle date and time data in RPG?

    • Answer: RPG uses specific data types and built-in functions for handling dates and times. Calculations and formatting of dates and times are done using specialized functions.

13. What are the different types of indicators in RPG?

    • Answer: Indicators are used for conditional logic and branching in RPG programs. They are essentially boolean flags that can be set and tested.

14. Explain the concept of chained files in AS400.

    • Answer: Chained files are used to link records together in a file based on a key field. This enables traversing through related records efficiently, especially for hierarchical data structures.

15. Describe your experience with database administration on AS400.

    • Answer: [This requires a personalized answer based on your experience. Mention specific tasks like creating and managing database files, defining indexes, backing up and restoring databases, user management, and performance monitoring.]

16. How familiar are you with AS400 security features?

    • Answer: [This requires a personalized answer. Mention knowledge of user profiles, authorities, roles, object security, and auditing features.]

17. What are your experiences with debugging AS400 programs?

    • Answer: [This requires a personalized answer. Mention your experience using debuggers, tracing program execution, analyzing error messages, and identifying code issues.]

18. Explain your understanding of the AS400's integrated file system.

    • Answer: The AS400's integrated file system is a key aspect of its architecture, offering a unified way to access and manage all types of data – from programs and libraries to databases and spooled files. This simplifies data management compared to systems with separate file systems.

19. How do you handle multi-threading in AS400 programs?

    • Answer: AS400's handling of multi-threading is different from other systems. It relies on job scheduling and multiple jobs to achieve parallel processing. Within a single RPG program, multi-threading is not directly supported in the same way as in other languages. Instead, techniques like using data queues or separate programs are typically employed.

20. What tools and utilities do you use for AS400 development?

    • Answer: [Mention specific tools like debuggers, code editors (like RDi), SQL development tools, and any other relevant tools used in your workflow.]

21. Describe your experience with working in a team environment on AS400 projects.

    • Answer: [This requires a personalized answer. Highlight your collaborative skills, your experience using source code management systems, and your ability to work with other developers effectively.]

22. What are your preferred methods for documenting AS400 code?

    • Answer: [Mention specific methods like in-line comments, separate documentation files, and using a documentation generation tool.]

23. Explain your experience with migrating AS400 applications to newer systems or technologies.

    • Answer: [This requires a personalized answer. Discuss experience with migration strategies, tools, and challenges involved in modernizing AS400 applications.]

24. How familiar are you with the concept of service programs in AS400?

    • Answer: Service programs group related procedures or modules together to enhance code reusability and modularity.

25. What is your understanding of AS400's database journaling?

    • Answer: Database journaling provides a mechanism for recovering data in case of system failures. It tracks changes made to the database, allowing for point-in-time recovery.

26. How do you handle performance bottlenecks in AS400 applications?

    • Answer: Use performance monitoring tools, analyze query plans, optimize SQL statements, adjust database indexes, improve program logic, and consider hardware upgrades if necessary.

27. What are your experiences with different RPG versions (e.g., RPG III, RPG IV, ILE RPG)?

    • Answer: [This requires a personalized answer. Discuss your proficiency with different RPG versions and their features.]

28. What are your experiences with using external APIs or interfaces with AS400 systems?

    • Answer: [This requires a personalized answer. Discuss experience with technologies like Web services, ODBC, JDBC, or other methods of external integration.]

29. How do you ensure data integrity in AS400 applications?

    • Answer: Use database constraints, validation rules, error checking, and data auditing to maintain data integrity.

30. Explain your understanding of AS400's object-oriented programming capabilities.

    • Answer: AS400 supports object-oriented programming through ILE (Integrated Language Environment) RPG. This enables modular design, code reusability, and encapsulation of data and methods.

31. What are some common challenges you've faced while working with AS400 systems?

    • Answer: [This requires a personalized answer. Discuss challenges related to older technology, limited resources, legacy code, and finding skilled developers.]

32. How do you stay updated with the latest AS400 technologies and best practices?

    • Answer: [Mention specific methods like attending conferences, reading technical publications, online courses, and engaging with online communities.]

33. Describe your experience with using version control systems for AS400 development.

    • Answer: [This requires a personalized answer. Mention experience with tools like Git, SVN, or other version control systems used for managing AS400 source code.]

34. How do you approach troubleshooting a program that is consuming excessive CPU resources on the AS400?

    • Answer: Use performance monitoring tools to identify the specific programs or processes consuming the CPU. Analyze code for inefficient loops or algorithms, and optimize SQL queries. Also examine system-level resource usage.

35. What is your experience with automating AS400 tasks?

    • Answer: [This requires a personalized answer. Discuss experience with scripting languages like CL, or using scheduling tools to automate tasks.]

36. Explain your understanding of the AS400's high availability features.

    • Answer: AS400 offers features like clustering and failover capabilities to ensure high availability and minimize downtime. This often involves using multiple systems to provide redundancy.

37. How do you handle database backups and recovery on AS400?

    • Answer: Use the system's built-in backup and recovery tools, employing appropriate strategies for full, incremental, and differential backups. Understand the process of restoring databases from backups.

38. What are your experiences with working with different database management systems (DBMS) on AS400?

    • Answer: [This requires a personalized answer. Discuss experience with DB2 for i and any other DBMS used on the AS400 platform.]

39. How do you ensure the security and compliance of AS400 applications?

    • Answer: Implement proper user access controls, follow security best practices, regularly audit security logs, use encryption where necessary, and stay up to date on security patches and updates.

40. Explain your understanding of AS400's integrated security features.

    • Answer: AS400 has built-in security features including user profiles, authorities, object security, and auditing capabilities that work together to protect data and resources.

41. How do you handle different character sets and code pages in AS400 applications?

    • Answer: Understand the different character sets and code pages used, and ensure consistent encoding throughout the application to avoid data corruption or display issues.

42. Describe your experience with using SQL/400 for database management.

    • Answer: [This requires a personalized answer. Detail your experience writing SQL queries, creating stored procedures, managing database objects, and using SQL for data manipulation and reporting.]

43. What is your understanding of the AS400's spool file system?

    • Answer: The spool file system manages output from programs, including reports, error messages, and other types of output. It allows for viewing, printing, and managing these output files.

44. Explain your experience with working with different AS400 operating system versions.

    • Answer: [This requires a personalized answer. Detail your experience with different OS versions and their specific features and limitations.]

45. How do you approach the design and development of a new AS400 application?

    • Answer: [This requires a personalized answer. Outline your development methodology, including requirements gathering, design, coding, testing, and deployment phases.]

46. What are your experiences with performance monitoring and optimization tools on AS400?

    • Answer: [This requires a personalized answer. Mention specific tools and techniques used for monitoring and optimizing application and database performance.]

47. Explain your understanding of the AS400's integrated message queue system.

    • Answer: The message queue system is used for asynchronous communication, enabling applications to exchange messages and communicate without direct coupling.

48. How do you handle data migration between different AS400 systems or databases?

    • Answer: Use tools and techniques for data extraction, transformation, and loading (ETL) processes, ensuring data integrity throughout the migration.

49. What are your experiences with working with external systems and integrating them with AS400 applications?

    • Answer: [This requires a personalized answer. Discuss experience with different integration methods, such as APIs, file transfers, and database links.]

50. How do you document your code to make it easier for others to understand and maintain?

    • Answer: Use clear and concise comments, meaningful variable names, well-structured code, and detailed documentation outlining the application's functionality and design.

51. Explain your approach to testing AS400 applications.

    • Answer: [This requires a personalized answer. Describe your testing methodology, including unit testing, integration testing, and user acceptance testing. Mention any automated testing techniques used.]

52. How familiar are you with the IBM Rational Developer for i (RDi)?

    • Answer: [This requires a personalized answer. Detail your experience using RDi for AS400 development, including its features and capabilities.]

53. What are your experiences with performance tuning SQL queries on AS400?

    • Answer: [This requires a personalized answer. Discuss techniques like query optimization, indexing, and analyzing query execution plans.]

54. How do you ensure the scalability of your AS400 applications?

    • Answer: Design applications with scalability in mind, considering database design, efficient algorithms, and using appropriate hardware resources.

55. Explain your understanding of the AS400's database partitioning techniques.

    • Answer: Database partitioning improves performance and scalability by distributing data across multiple partitions. This technique is useful for very large databases.

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