DP-300 Practice Question: Monitor, configure, and optimize database resources
You are a database administrator for an e-commerce company that uses Azure SQL Managed Instance. You have a database that experiences high blocking due to long-running transactions. You need to configure a solution that automatically terminates the blocking process after it has been waiting for more than 5 seconds. The solution should be set at the database level and should not require any application changes. What should you do?
⚠ Common exam trap
A common trap is to assume LOCK_TIMEOUT terminates the blocking transaction, but it actually kills the waiting query. The blocker continues to hold locks.
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
✓
Set the DEADLOCK_PRIORITY to LOW on the blocking session and set LOCK_TIMEOUT to 5000.
LOCK_TIMEOUT can be used to automatically terminate a query that has been waiting for a lock longer than a specified number of milliseconds. Setting LOCK_TIMEOUT to 5000 will kill the waiting (blocked) session after 5 seconds, which mitigates blocking. While LOCK_TIMEOUT is a session-level setting, it can be applied database-wide by using a logon trigger or by setting server-level defaults without modifying application code. Resource Governor does not have a MAX_GRANT_TIME setting for T-SQL queries, so option B is invalid. RCSI and snapshot isolation reduce blocking but do not terminate long-running transactions, and setting the isolation level for all sessions requires application changes or connection settings.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable read committed snapshot isolation (RCSI) on the database.
Why it's wrong here
Enabling read committed snapshot isolation reduces writer blocking readers but does not terminate long-running blocking transactions. It changes the behavior of read queries, not the blocking process itself.
- ✗
Create a resource governor workload group with a maximum grant time of 5 seconds.
Why it's wrong here
Resource Governor workload groups with a maximum grant time automatically terminate queries that exceed the specified time, effectively terminating blocking processes. This is set at the database level and requires no application changes.
- ✓
Set the DEADLOCK_PRIORITY to LOW on the blocking session and set LOCK_TIMEOUT to 5000.
Why this is correct
Setting DEADLOCK_PRIORITY to LOW and LOCK_TIMEOUT to 5000 does not terminate the blocking transaction; LOCK_TIMEOUT kills the waiting query. Also, DEADLOCK_PRIORITY is a session-level setting, requiring application changes, which violates the requirement.
- ✗
Set the transaction isolation level to SNAPSHOT for all sessions.
Why it's wrong here
Setting the transaction isolation level to SNAPSHOT for all sessions provides row versioning for reads, reducing some blocking, but does not automatically terminate blocking processes. It requires changes to session settings, not a database-level configuration.
Go deeper
Related to this question
Learn chapter
Overview of Azure Data Platform Options
Key term
Azure SQL Managed Instance
Azure SQL Managed Instance is a fully managed cloud database service that gives you nearly all the features of Microsoft SQL Server on your own server, without you having to manage the hardware or operating system.
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Written by Johnson Ajibi, MSc IT Security
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