ABAP Core

Lessons in this topic

• ABAP Program Structure and Runtime FlowUnderstand how a classical ABAP report starts, flows and executes in real SAP systems.
• Selection Screen: PARAMETERS, SELECT-OPTIONS and ValidationBuild safe selection screens with mandatory inputs, ranges and user-friendly validations.
• ABAP Data Types and LiteralsElementary types, packed decimals, string vs char, and when to use TYPES vs DATA.
• Control Flow and String TemplatesIF/CASE, LOOP AT variants, and modern string templates.
• System Fields: sy-subrc, sy-tabix, sy-datum, sy-ucommUnderstand the most-used ABAP system fields and how they affect program logic.
• Messages and User-Friendly Error HandlingLearn how to show clear business messages instead of confusing technical errors.
• DATA, TYPES, CONSTANTS and VALUE OperatorLearn how to declare variables, structures, constants and initial values safely.
• Operators, Expressions and Type ConversionUse ABAP expressions and conversions safely in business logic.
• TRY CATCH and Exception Handling BasicsHandle runtime errors safely using class-based exceptions and fallback logic.
• Clean ABAP Basics for Maintainable CodeWrite ABAP that is readable, testable and easier for other consultants to maintain.

Interview questions covered

• You put a breakpoint in a custom program but it's never hit even though you're sure the code path is being executed. What are the possible reasons and how do you debug this systematically?
• What are the different types of internal tables in ABAP (Standard, Sorted, Hashed) and what access performance characteristics does each have?
• In a production support ticket, users report that a custom Z-program sometimes shows the wrong currency conversion for cross-company transactions, but it works fine most of the time. How would you approach troubleshooting this intermittent issue?
• You're told that a report gives correct output in the foreground (SE38, F8) but wrong output when scheduled as a background job. What categories of causes would you investigate?
• A background job processing 100,000 records dumps with a TIME_OUT or memory-related short dump after running for hours, but the same logic works fine for a smaller test file. How do you debug and fix this without being able to reproduce it interactively?
• You are asked to review a proposed technical design where a custom real-time interface calls an external REST API synchronously from inside a core SD sales order save user exit for every order, to fetch a fraud score before allowing save. As the architect, what concerns would you raise?
• You're reviewing a colleague's custom ALV report that dynamically builds a field catalog based on customizing settings, and it occasionally shows incorrect column headers or wrong data types for certain configurations. How would you approach root-causing this dynamic field catalog issue?
• What is the difference between a Function Module and a Method of a Class? When would you choose one over the other in a new development?
• A custom interface program uses a Z-table as a staging area and inserts millions of rows daily, purging old data periodically. Over time, the table's performance has degraded significantly even for simple SELECTs by key. What would you investigate and recommend?
• Your custom Z-report joins three large custom Z-tables using nested SELECTs and it's slow. The functional team says all three tables are needed together frequently across multiple reports. What performance and design options would you consider, including database-level options?
• What is the difference between a Data Dictionary structure, a TYPE created in ABAP program, and a database table? When would you use each in a real project?
• You are asked to build an interface that receives 50,000 material records daily from a third-party system and update material master data. What ABAP design considerations would you keep in mind to ensure this runs reliably every day?
• You are designing a custom module pool transaction that must handle both online (dialog) entry and a mass upload of thousands of records via a background program, using the same business validation logic. How would you architect this to avoid code duplication and ensure performance in both modes?
• Explain the difference between SELECT SINGLE, SELECT INTO TABLE, and SELECT ... ENDSELECT. Why is looping with SELECT...ENDSELECT generally discouraged in production code?
• A custom class-based exception is being raised deep inside a call stack (Class A calls Class B calls Class C), but the calling program only shows a generic 'exception occurred' message without the actual root cause detail. How would you debug and improve this?
• A background job that processes vendor payments occasionally fails with a lock table overflow (enqueue) error, especially during month-end. How would you diagnose and resolve this?
• Your team inherited a legacy custom program full of nested PERFORM subroutines with heavy use of global variables. The business now wants to add new functionality and unit test it. How would you approach refactoring this safely without breaking existing functionality?
• A new joiner on your team wrote a custom program using nested loops (LOOP inside LOOP) to match sales orders against delivery data, and it works fine in dev with 100 records but times out in production with 200,000 records. How do you explain the issue and guide them to a fix?
• A custom report that used to run in 2 minutes is now taking 45 minutes after go-live volume increased. The report reads material master data in a loop using SELECT SINGLE inside a loop over sales items. How would you approach diagnosing and fixing this?
• During debugging, you notice that a work area's value changes unexpectedly between two statements even though no explicit assignment happens between them in the code you're viewing. What could cause this and how would you find the actual culprit?

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