SAP-C02 Practice Question: Accelerate Workload Migration and Modernization
During an on-premises to AWS migration using AWS MGN (Application Migration Service), the replication is stuck at 99% for the last few GB. The source server is a Linux database server with a large InnoDB redo log. What is the most likely cause?
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
✓
Continuous writes to the database redo logs preventing final sync
AWS MGN uses changed block tracking (CBT) to replicate changed blocks. Large InnoDB redo logs are continuously written, causing constant changes and preventing final sync. Option A (High disk I/O) can slow replication but would not cause a stall at exactly 99%. Option B (source server reboot) is not required after agent installation and would reset replication, not stall at 99%. Option C (insufficient network bandwidth) would affect all stages, not just final sync. Therefore, continuous writes to the redo logs (Option D) is the most likely cause.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
High disk I/O on the source server
Why it's wrong here
High disk I/O slows snapshot reads but does not pin progress at 99%; the constant redo log writes keep generating new blocks for MGN to ship, so the final delta never drains. It is tempting because I/O contention is a common migration bottleneck, and would be correct if throughput were merely degraded rather than stalled.
- ✗
The source server needs reboot after MGN agent installation
Why it's wrong here
A reboot does not resolve a stall at 99%; MGN agents install and run without requiring one, and replication would have failed far earlier. It is tempting because reboots commonly fix agent or driver issues on Windows sources, and would be correct if the agent had just been installed and services were not yet running.
- ✗
Insufficient network bandwidth between source and AWS
Why it's wrong here
Bandwidth starvation throttles throughput throughout replication, not only the final few gigabytes; a stall at 99% on a database server points to the InnoDB redo log being continuously written, so the delta never converges. It is tempting because bandwidth is the usual suspect for slow MGN replication, and would be correct if the whole transfer were crawling.
- ✓
Continuous writes to the database redo logs preventing final sync
Why this is correct
Continuous InnoDB redo log writes mean the source volume never reaches a quiescent state, so MGN's final sync cannot converge — each pass replicates new blocks faster than they drain. The 99% stall reflects this ongoing delta, not a network or staging-area fault. Quiescing the database or stopping writes lets the final cutover complete.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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