PAS-C01 Operations and Maintenance Practice Question
This PAS-C01 practice question tests your understanding of operations and maintenance. 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 company runs SAP on AWS and uses a Multi-AZ RDS for SAP ASE database. The operations team receives an alert that the database instance failed over automatically. After the failover, the SAP application servers are unable to connect to the database. The team checks the RDS console and sees that the DB instance status is 'available' and the endpoint is the same as before. The security groups and network ACLs have not changed. What is the MOST likely reason for the connectivity issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The application servers have cached the old database IP address and need to flush DNS.
Option A is correct because after a failover, the DNS record for the RDS endpoint is updated to point to the new primary, but the application may still be using the old IP due to DNS caching. Option B is wrong because the endpoint remains the same. Option C is wrong because Multi-AZ failover updates the DNS record. Option D is wrong because the failover does not change the security group.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The RDS endpoint changed after the failover.
Why it's wrong here
The endpoint CNAME remains the same.
✓
The application servers have cached the old database IP address and need to flush DNS.
The security group for the database instance no longer allows traffic from the application servers.
Why it's wrong here
Security groups remain unchanged.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PAS-C01 ACL questions on filtering logic and placement.
Operations and Maintenance — This question tests Operations and Maintenance — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The application servers have cached the old database IP address and need to flush DNS. — Option A is correct because after a failover, the DNS record for the RDS endpoint is updated to point to the new primary, but the application may still be using the old IP due to DNS caching. Option B is wrong because the endpoint remains the same. Option C is wrong because Multi-AZ failover updates the DNS record. Option D is wrong because the failover does not change the security group.
What should I do if I get this PAS-C01 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PAS-C01 ACL questions on filtering logic and placement.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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