Databricks-DE-Assoc Troubleshooting, Monitoring, and Optimization Practice Question
Exhibit
Error: [DELTA_FILE_NOT_FOUND] The file /mnt/data/_delta_log/00000000000000000005.json was not found.
Refer to the exhibit. A job fails with the provided error message. What is the most likely cause of this failure in a Databricks Delta Lake environment?
⚠ Common exam trap
Candidates often assume the error is related to network connectivity or cluster permissions. They overlook the relationship between long-running jobs and the aggressive deletion of files by the VACUUM command.
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 VACUUM retention threshold was set too low.
This error occurs when the Delta log entries point to files that no longer exist, typically caused by a VACUUM operation running with a retention period shorter than the time required for long-running streaming jobs to finish. When a file is physically deleted by VACUUM, but a reader still references it via the transaction log, the read operation fails because the file object is inaccessible in the underlying storage.
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 Delta table has reached the maximum file limit.
Why it's wrong here
Delta Lake does not have a hard limit on the number of files in a table that would cause a 'file not found' error. This error is strictly related to physical file availability as tracked by the transaction log, not the total volume of files in the storage location.
- ✓
The VACUUM retention threshold was set too low.
Why this is correct
Setting the VACUUM retention period shorter than the time a long-running process needs to access old data leads to failures. If a process is mid-read while a concurrent VACUUM deletes files, the reader will be unable to locate the necessary data files, resulting in the reported error.
- ✗
The cluster running the job lacks proper IAM permissions.
Why it's wrong here
IAM permission issues typically manifest as AccessDenied errors or 403 Forbidden status codes. A 'file not found' error specifically indicates that the file path is known to the system but the physical object is missing from the underlying storage layer, which is a data lifecycle management issue.
- ✗
The transaction log is corrupted and requires manual deletion.
Why it's wrong here
Manually deleting transaction log files is rarely the correct solution and often leads to irreparable table corruption. The system tracks files via the log, and if a file is missing, fixing the log will not restore the underlying data file that was physically removed from storage.
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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 Databricks exam blueprint
This Databricks-DE-Assoc practice question is part of Courseiva's free Databricks 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 Databricks-DE-Assoc exam.