C100DBA Server Administration Practice Question
Which THREE metrics provided by the 'mongostat' utility are most helpful for identifying a performance bottleneck caused by a high volume of concurrent write operations?
⚠ Common exam trap
Candidates often select metrics like 'res' or 'faults' which relate to memory rather than the write queue, missing the direct correlation between 'qw' and write congestion.
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
✓
insert
Monitoring server health via mongostat is a daily task for a DBA. High write volumes are best identified by looking at the actual operation counts (insert, update, delete) and the state of the write queue. If the 'qw' (queue write) count is high, it indicates that the storage engine cannot keep up with the incoming write requests.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
insert
Why this is correct
The 'insert' column shows the number of insert operations per second. A high value in this column directly indicates a high write load. For a DBA, monitoring this metric alongside others helps determine if the current hardware and storage engine configuration are sufficient for the application's write throughput requirements.
- ✗
getmore
Why it's wrong here
The 'getmore' metric tracks the number of operations that retrieve additional data from a cursor, typically used in large read queries or tailing the oplog. While important for read performance, it does not provide direct insight into the volume or pressure of write operations on the database server.
- ✓
qw
Why this is correct
The 'qw' column stands for 'queue write' and represents the number of write operations waiting for a lock or storage engine availability. A consistently non-zero value in this column is a strong indicator that the server is experiencing a write bottleneck and cannot process requests fast enough.
- ✗
vsize
Why it's wrong here
The 'vsize' metric indicates the total virtual memory size used by the mongod process. While it is a useful indicator of overall memory usage, it is not a specific measure of write activity or write-related bottlenecks, as virtual memory includes mapped files and other overhead unrelated to current operation throughput.
- ✓
update
Why this is correct
The 'update' column tracks the number of update operations per second. Since updates are write operations that often involve both a read and a write to the data files and indexes, they contribute significantly to the write load. Tracking this metric is essential for understanding the overall write pressure.
About these practice questions
Courseiva writes every C100DBA question from scratch — 222 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official MongoDB exam blueprint
This C100DBA practice question is part of Courseiva's free MongoDB 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 C100DBA exam.