The correct course of action is to proceed with the custom ETL script after thorough testing and validation. This is the best choice because custom ETL scripts are a standard technical solution when legacy data formats are incompatible with a new ERP system, but their success hinges on rigorous validation to ensure data integrity, completeness, and accuracy during migration. On the CISA exam, this scenario tests your understanding of the balance between project efficiency and risk management—specifically, that a custom ETL script for data migration validation is acceptable only when paired with formal testing protocols, not simply because it saves time. A common trap is assuming that any automated script is inherently reliable, whereas the auditor’s focus must remain on verifying that transformation rules preserve data fidelity. Remember the memory tip: “Test before you trust the transform”—validation is the non-negotiable gatekeeper for any custom ETL approach.
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.
During the implementation of a new ERP system, the project team discovers that the legacy system data cannot be directly migrated due to incompatible data formats. The project manager proposes building a custom script to extract, transform, and load (ETL) data. Which of the following is the BEST course of action?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Proceed with the custom ETL script after thorough testing and validation.
Option C is correct because building a custom ETL script is a common and acceptable approach when legacy data formats are incompatible with a new ERP system. The key is that the script must undergo thorough testing and validation to ensure data integrity, completeness, and accuracy before migration. This balances the need for timely implementation with the risk of data corruption, which can be mitigated through rigorous quality assurance processes.
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.
✗
Manually re-enter all legacy data into the new system.
Why it's wrong here
Manual re-entry is inefficient and error-prone.
✗
Delay the implementation until a commercial migration tool is available.
Why it's wrong here
Unnecessary delay; alternatives exist.
✓
Proceed with the custom ETL script after thorough testing and validation.
Why this is correct
Custom ETL is appropriate with proper validation.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Abandon the legacy data and start fresh in the new system.
Why it's wrong here
Loss of historical data is not advisable.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume custom scripts are inherently risky and choose to delay or abandon data, failing to recognize that with proper testing and validation, custom ETL is a standard and effective solution for incompatible data formats.
Detailed technical explanation
How to think about this question
ETL scripts typically handle data type conversions, normalization, and cleansing using languages like Python, SQL, or specialized ETL platforms (e.g., Talend, Apache NiFi). A subtle behavior is that date/time formats, character encodings (e.g., ASCII vs. UTF-8), and null value representations often cause silent data corruption if not explicitly mapped. In a real-world ERP migration, a custom script might need to parse legacy COBOL copybooks or flat files with fixed-width fields, requiring careful handling of padding and delimiters to avoid truncation or misalignment.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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: Proceed with the custom ETL script after thorough testing and validation. — Option C is correct because building a custom ETL script is a common and acceptable approach when legacy data formats are incompatible with a new ERP system. The key is that the script must undergo thorough testing and validation to ensure data integrity, completeness, and accuracy before migration. This balances the need for timely implementation with the risk of data corruption, which can be mitigated through rigorous quality assurance processes.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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