DP-300 Practice Question: Monitor, configure, and optimize database resources
Exhibit
Refer to the exhibit. SELECT wait_type, wait_time_ms, waiting_tasks_count FROM sys.dm_os_wait_stats WHERE wait_type = 'PAGEIOLATCH_SH' ORDER BY wait_time_ms DESC;
You run the query in the exhibit on an Azure SQL Database. The result shows high wait_time_ms for PAGEIOLATCH_SH waits. What does this indicate?
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
✓
I/O subsystem bottleneck for read operations
PAGEIOLATCH_SH waits indicate that a query is waiting for a data page to be read from disk into the buffer pool, which is an I/O operation. High wait_time_ms for this wait type typically points to an I/O subsystem bottleneck for read operations, making option A correct. Option B (CPU bottleneck) is incorrect because PAGEIOLATCH_SH is related to I/O, not CPU. Option C (blocking) is incorrect because blocking is associated with LOCK waits, not PAGEIOLATCH_SH. Option D (memory pressure) is incorrect; while memory pressure can increase physical I/O, the wait type itself specifically indicates I/O latency for reading pages from disk.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
I/O subsystem bottleneck for read operations
Why this is correct
PAGEIOLATCH_SH waits occur when waiting for I/O to complete for reading pages.
- ✗
CPU bottleneck
Why it's wrong here
CPU waits are different, like SOS_SCHEDULER_YIELD.
- ✗
Blocking between concurrent transactions
Why it's wrong here
Blocking is indicated by LCK_M_* waits.
- ✗
Memory pressure
Why it's wrong here
PAGEIOLATCH_SH indicates I/O, not memory.
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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