C100DBA Server Administration Practice Question
Exhibit
2023-10-27T10:00:00.000Z I STORAGE [conn12] WiredTiger (28) No space left on device 2023-10-27T10:00:01.000Z F STORAGE [conn12] Failed to write record to storage engine
Refer to the exhibit. The MongoDB process has crashed due to a storage engine error. What is the most immediate administrative action required to restore service?
⚠ Common exam trap
Exams often lure candidates into attempting a database repair operation first, failing to realize that full disks require immediate space freeing before any recovery command can execute.
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
✓
Expand the disk volume and restart the mongod process.
The error 'No space left on device' indicates that the disk partition hosting the 'dbPath' directory is completely full. This prevents WiredTiger from writing data, metadata, or logs, causing an immediate shutdown to prevent data corruption. Administrators must free up space on the disk or extend the partition before restarting the service, as the database cannot recover or accept new writes without sufficient storage capacity to manage its internal files.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Run 'db.repairDatabase()' via the shell to free up space.
Why it's wrong here
The repair command requires additional disk space to create temporary files for the restoration process. If the disk is already completely full, running repair will immediately fail and may further damage the data files. This command is not a solution for lack of available disk capacity.
- ✗
Clear the 'journal' directory files to recover space.
Why it's wrong here
Manually deleting journal files is extremely dangerous and will result in data corruption. These files are essential for ensuring the integrity of the data files after a restart. Deleting them compromises the ACID properties of the database and is never a recommended administrative recovery procedure.
- ✓
Expand the disk volume and restart the mongod process.
Why this is correct
Expanding the underlying disk volume provides the necessary storage capacity for the database to function. Once additional space is available, the WiredTiger engine can successfully initialize, perform recovery using the journal, and resume normal operations. This is the only safe way to resolve an 'out of space' failure.
- ✗
Modify the 'storage.wiredTiger.engineConfig.cacheSizeGB' setting in the config file.
Why it's wrong here
The WiredTiger cache size configures how much RAM the database uses, not the physical disk storage. Reducing the cache size will not free up disk space for data files or logs, and therefore will not resolve the 'No space left on device' error occurring at the filesystem level.
About these practice questions
This C100DBA question is part of Courseiva's 222-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam 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.