PAS-C01 Operations and Maintenance Practice Question
A company runs SAP on AWS and uses a Multi-AZ RDS for Oracle as the database. They observe that the database failover took longer than expected during a recent test. What is the most likely cause of the increased failover time?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The primary instance had a high volume of ongoing transactions that needed to be completed or rolled back before failover could proceed.
In a Multi-AZ RDS deployment, during a failover, the primary instance must complete or roll back any in-flight transactions before the standby can take over. If there is a high volume of ongoing transactions, this process can take longer, increasing failover time. Option A is incorrect because uncommitted transactions are typically rolled back quickly; the issue is more about transactions that need to reach a consistent state. Option B is incorrect because DNS TTL does not significantly affect RDS failover detection; the failover mechanism uses a CNAME update that is fast. Option D is incorrect because in Multi-AZ RDS, the standby is kept in sync synchronously, and read replicas are not used for Multi-AZ; they are a separate feature.
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 database had a large number of uncommitted transactions that needed to be rolled back.
Why it's wrong here
Uncommitted transactions are handled during failover but are not the primary cause of delay.
- ✗
The DNS TTL was set too high, causing delays in routing to the new primary.
Why it's wrong here
RDS Multi-AZ uses a CNAME, and DNS TTL is typically 60 seconds; not the major cause.
- ✓
The primary instance had a high volume of ongoing transactions that needed to be completed or rolled back before failover could proceed.
Why this is correct
RDS waits for pending transactions to complete, which can increase failover time.
- ✗
The standby instance was not in sync because read replicas were used for reads.
Why it's wrong here
Multi-AZ uses synchronous replication; read replicas are separate.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PAS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PAS-C01 exam.