LFCS Operation of Running Systems Practice Question
This LFCS practice question tests your understanding of operation of running systems. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Exhibit
Refer to the exhibit.
Tasks: 120 total, 1 running, 119 sleeping, 0 stopped, 0 zombie
%Cpu(s): 8.3 us, 2.0 sy, 0.0 ni, 89.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 8092260 total, 1025468 free, 3892240 used, 3774552 buff/cache
KiB Swap: 2097148 total, 2097148 free, 0 used. 3598988 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5678 wwwdata 20 0 556240 89748 22012 S 0.3 1.1 0:00.12 nginx
9101 mysql 20 0 1874452 102456 18520 S 0.0 1.3 0:05.34 mysqld
1234 root 20 0 305600 6428 3920 S 0.0 0.1 0:00.01 systemd
Based on the exhibit, which process is using the most physical memory (RES)?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
mysqld (PID 9101)
The exhibit shows the output of the `top` command, where the RES column indicates the resident memory (physical RAM) used by each process. mysqld (PID 9101) has a RES value of 2.5g, which is significantly higher than nginx (PID 5678) with 128m and systemd (PID 1234) with 48m, making it the process using the most physical memory.
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.
✓
mysqld (PID 9101)
Why this is correct
RES is 102456, the highest among listed processes.
Related concept
Read the scenario before looking for a memorised answer.
✗
Not determinable from exhibit
Why it's wrong here
The exhibit clearly shows RES values.
✗
nginx (PID 5678)
Why it's wrong here
RES is 89748, lower than mysqld.
✗
systemd (PID 1234)
Why it's wrong here
RES is 6428, very low.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse the VIRT (virtual memory) column with RES, or assume that a process with a higher PID or name familiarity uses more memory, rather than reading the RES values directly from the exhibit.
Trap categories for this question
Command / output trap
The exhibit clearly shows RES values.
Detailed technical explanation
How to think about this question
The RES column in `top` represents resident memory, which is the portion of a process's virtual address space currently held in physical RAM, excluding swapped-out pages. Under the hood, the kernel tracks this via the /proc/[pid]/status file's VmRSS field, and a high RES value often indicates a database or memory-intensive application like MySQL that caches data in memory for performance. In real-world scenarios, monitoring RES helps identify memory leaks or processes consuming excessive RAM, which can trigger OOM (Out-Of-Memory) killer if the system runs out of physical memory.
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 practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
Operation of Running Systems — This question tests Operation of Running Systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: mysqld (PID 9101) — The exhibit shows the output of the `top` command, where the RES column indicates the resident memory (physical RAM) used by each process. mysqld (PID 9101) has a RES value of 2.5g, which is significantly higher than nginx (PID 5678) with 128m and systemd (PID 1234) with 48m, making it the process using the most physical memory.
What should I do if I get this LFCS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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