DP-300 Practice Question: Monitor, configure, and optimize database resources
Exhibit
Azure CLI output from 'az sql db list-editions -o table': Edition | SLO | DTU | MaxStorageGB GeneralPurpose | GP_Gen5_2 | 100 | 512 GeneralPurpose | GP_Gen5_4 | 200 | 512 GeneralPurpose | GP_Gen5_8 | 400 | 1024 BusinessCritical | BC_Gen5_2 | 100 | 512 BusinessCritical | BC_Gen5_4 | 200 | 512 Current database properties: Name: SalesDB Edition: GeneralPurpose ServiceObjective: GP_Gen5_2 Storage used: 480 GB Max storage: 512 GB Query Store shows: Total log write rate: 5 MB/s Log IO percentage: 80% sys.dm_db_log_space_usage: Total log space: 100 GB Used log space: 95 GB
Refer to the exhibit. The SalesDB database is experiencing log space full errors. Based on the exhibit, what is the most likely reason?
⚠ Common exam trap
The trap here is that candidates see 'log space full' and immediately think of storage capacity issues (Option A) or performance throttling (Option C), but the exhibit clearly shows the data file has free space, directing the focus to log truncation failure as the root 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
✓
The transaction log is not being truncated, possibly due to an active transaction or replication
The exhibit shows a transaction log with very low free space (0.01%) and a high log used percentage (99.99%), but the data file has ample free space. This indicates the transaction log is not being truncated, likely due to an active transaction preventing log reuse or a replication scenario that marks log records as needed. In Azure SQL Database, log space is managed automatically, but long-running transactions or replication can block log truncation, causing log space full errors even when storage is not full.
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 database storage is almost full, preventing log growth
Why it's wrong here
Data file has 32 GB free; log space is separate.
- ✓
The transaction log is not being truncated, possibly due to an active transaction or replication
Why this is correct
High used log space with high write rate suggests truncation issue.
- ✗
The log rate limit is being throttled due to high log IO percentage
Why it's wrong here
Log IO percentage indicates consumption, not throttling.
- ✗
The database should be scaled to BusinessCritical tier for faster log writes
Why it's wrong here
Scaling tier does not fix log truncation issue.
Go deeper
Related to this question
Learn chapter
Overview of Azure Data Platform Options
Key term
Azure SQL Performance Tuning
Azure SQL Performance Tuning is the process of optimizing the speed and efficiency of queries and database operations in Microsoft Azure SQL Database or SQL Managed Instance to reduce latency and improve throughput.
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Written by Johnson Ajibi, MSc IT Security
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