The answer is reconciliation of converted data totals to source system totals because this control directly verifies that every record from the legacy system has been accurately migrated without loss or duplication. By comparing aggregate values such as account balances and transaction counts between the source and target databases, this data conversion reconciliation provides a definitive check for completeness and accuracy that no other control can guarantee. On the Certified Information Systems Auditor CISA exam, this concept tests your understanding of the most critical control during a data conversion project—a common scenario where candidates mistakenly choose input validation or access controls instead. A frequent trap is assuming that parallel testing or data mapping alone suffices, but only reconciliation of control totals catches silent errors like dropped records or double-counting. Remember the mnemonic: “Totals tell the tale—reconcile or fail.”
CISA Practice Question: Information Systems Acquisition, Development and Implementation
This CISA practice question tests your understanding of information systems acquisition, development and implementation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A bank is converting data from its legacy core banking system to a new platform. Which control is MOST critical to ensure the completeness and accuracy of data conversion?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Reconciliation of converted data totals to source system totals
Reconciliation of converted data totals to source system totals is the most critical control because it directly verifies that every record from the legacy system has been accurately migrated without loss or duplication. This control compares aggregate values (e.g., account balances, transaction counts) between the source and target databases, providing a definitive check for completeness and accuracy that other controls cannot guarantee.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Parallel running of both systems
Why it's wrong here
Parallel running helps but is not specifically for data conversion accuracy.
✓
Reconciliation of converted data totals to source system totals
Why this is correct
Reconciliation directly verifies completeness and accuracy.
Related concept
Read the scenario before looking for a memorised answer.
✗
Data validation rules programmed in the conversion tool
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse 'data validation rules' (which ensure individual field correctness) with 'reconciliation' (which ensures aggregate completeness and accuracy), leading them to choose Option C even though validation cannot detect missing records or totals.
Detailed technical explanation
How to think about this question
Reconciliation typically involves running SQL aggregation queries (e.g., SUM, COUNT) on both the legacy and new databases, then comparing hash totals or control totals for key fields like account balances or customer IDs. In practice, a bank might use a reconciliation script that computes a checksum over all account numbers and balances, ensuring that the cryptographic hash of the source data matches the target, which catches even single-bit errors. This control is often automated and executed immediately after the conversion load, before any user access is granted.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the CISA exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Information Systems Acquisition, Development and Implementation — This question tests Information Systems Acquisition, Development and Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Reconciliation of converted data totals to source system totals — Reconciliation of converted data totals to source system totals is the most critical control because it directly verifies that every record from the legacy system has been accurately migrated without loss or duplication. This control compares aggregate values (e.g., account balances, transaction counts) between the source and target databases, providing a definitive check for completeness and accuracy that other controls cannot guarantee.
What should I do if I get this CISA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Variation 1. A company is migrating from a legacy system to a cloud-based ERP. Which of the following is the MOST important control to ensure data integrity during data conversion?
easy
A.Automated backup
B.User acceptance testing
C.Parallel running
✓ D.Reconciliation of control totals
Why D: Reconciliation of control totals is the most important control because it directly verifies that the sum of key fields (e.g., total account balances, record counts) in the source system matches the target cloud-based ERP after conversion. This ensures no data is lost, duplicated, or corrupted during the extraction, transformation, and loading (ETL) process, which is critical for maintaining data integrity in a migration from a legacy system.
Last reviewed: Jun 25, 2026
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