Data Warehousing on AWS Training Data Warehousing on AWS: Workload Management 2 — Questions and Answers
Question 1: In Amazon Redshift WLM, what happens to a query that exceeds its queue's concurrency limit?
- It is immediately cancelled
- It is placed in a waiting queue until a slot opens (Correct answer)
- It is automatically routed to a different queue
- It is executed with reduced priority
Correct answer: It is placed in a waiting queue until a slot opens
When all concurrency slots in a WLM queue are occupied, additional queries wait in the queue until a slot becomes available.
Question 2: Which Redshift WLM parameter controls how many queries can execute simultaneously in a single queue?
- Query slots count (Correct answer)
- Memory percentage
- Timeout value
- Queue priority
Correct answer: Query slots count
The query slots count (concurrency level) in a WLM queue determines how many queries can run simultaneously in that queue.
Question 3: What is the maximum number of WLM queues you can configure in Amazon Redshift manual WLM?
- 5
- 8 (Correct answer)
- 10
- 16
Correct answer: 8
Amazon Redshift manual WLM allows a maximum of 8 queues, plus the default queue.
Question 4: A query group label is used in Redshift WLM to accomplish which of the following?
- Assign a user to a specific IAM role
- Route a query session to a specific WLM queue (Correct answer)
- Limit the amount of data scanned by a query
- Set the compression encoding for query results
Correct answer: Route a query session to a specific WLM queue
Setting a query group label via SET query_group allows sessions to be routed to the WLM queue configured with that matching label.
Question 5: In Redshift automatic WLM, how does the system determine memory and concurrency allocation?
- Administrators manually set fixed values per queue
- Redshift dynamically adjusts based on query complexity and cluster resources (Correct answer)
- AWS Support configures it during cluster provisioning
- It uses static defaults that cannot be changed
Correct answer: Redshift dynamically adjusts based on query complexity and cluster resources
Automatic WLM uses machine learning to dynamically adjust concurrency and memory allocation based on workload characteristics and available cluster resources.
Question 6: Which SVL system view in Redshift can be queried to see the WLM queue a completed query was assigned to?
- SVL_QUERY_REPORT
- SVL_QLOG
- SVL_WLM_QUERY_QUEUE_INFO (Correct answer)
- SVL_COMPILE
Correct answer: SVL_WLM_QUERY_QUEUE_INFO
SVL_WLM_QUERY_QUEUE_INFO records details about completed queries including the WLM queue they were routed to and wait times.
Question 7: What is the effect of setting WLM timeout to 0 for a queue in Amazon Redshift?
- Queries are immediately cancelled upon submission
- No timeout is applied and queries run until completion (Correct answer)
- Queries are limited to 1 second of execution
- The queue is disabled
Correct answer: No timeout is applied and queries run until completion
A WLM timeout value of 0 means no timeout is enforced, allowing queries in that queue to run indefinitely until they complete or are manually cancelled.
Data Warehousing on AWS Training Data Warehousing on AWS: Workload Management 2
In Amazon Redshift WLM, what happens to a query that exceeds its queue's concurrency limit?