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質問 1：
In PolarDB, if an UPDATE SQL statement encounters an issue, you need to check the execution plan to figure out the root cause. However, in the production environment, to avoid affecting the production data, what statement should you use to view the execution plan? (Number of correct answers: 2)
A. explain analyze SQL
B. explain verbose SQL
C. explain SQL
D. explain analyze verbose SQL
正解：A,B
質問 2：
During the process of backing up an RDS database, a developer found that the backup failed. What might cause this to happen?
A. DML operations were performed during the backup
B. The database instance is not stopped
C. DDL operations were performed during the backup
D. DCL operations were performed during the backup
正解：A
質問 3：
Which of the following operations can be performed through Log Service sAPI? (Number of correct answers:
3)
A. Access control for different users
B. Create a Logstore, write and read logs to the Logstore
C. Collect logs based on Logtail configuration and Logtail machine group information
D. Deliver logs to OSS for storage and analysis
正解：A,B,C
質問 4：
Alibaba Cloud Content Delivery Network (CDN) is a suitable product for the following scenarios: (Number of correct answers: 2)
A. Images, HTML, CSS and JS files on a medium-sized E-commerce website.
B. News websites with more than 30 million daily page views and users are all from Singapore.
C. Static sites with more than 100,000 daily page views.
D. BBS forums with less than 100 daily page views.
正解：B,D
質問 5：
A developer recently discovered that their company's application is beginning to suffer performance degradation as a result of increased user demand for the application. After some analysis, the major bottleneck is discovered to be the RDS database instance which hosts the company's databases, "A" and "B". The developer plans to use the DTS data migration solution to move one of the databases to a new RDS instance.
Which of the following statements is correct? (Number of correct answers: 3)
A. The database account used for data migration must have read and write permissions. To ensure database security, please delete the database account used for data migration or reclaim related write permissions after data migration is completed.
B. The code for the application will have to be rewritten once this migration is complete.
C. Create a reverse data migration task and start it to migrate subsequent incremental data from target Instance database B to source instance database B.
D. After disconnecting the connection between the source instance database B and the application, you need to log in to the source database B to check the session messages to ensure that no new sessions performed write operations.
正解：A,B,D
In PolarDB, if an UPDATE SQL statement encounters an issue, you need to check the execution plan to figure out the root cause. However, in the production environment, to avoid affecting the production data, what statement should you use to view the execution plan? (Number of correct answers: 2)
A. explain analyze SQL
B. explain verbose SQL
C. explain SQL
D. explain analyze verbose SQL
正解：A,B
質問 2：
During the process of backing up an RDS database, a developer found that the backup failed. What might cause this to happen?
A. DML operations were performed during the backup
B. The database instance is not stopped
C. DDL operations were performed during the backup
D. DCL operations were performed during the backup
正解：A
質問 3：
Which of the following operations can be performed through Log Service sAPI? (Number of correct answers:
3)
A. Access control for different users
B. Create a Logstore, write and read logs to the Logstore
C. Collect logs based on Logtail configuration and Logtail machine group information
D. Deliver logs to OSS for storage and analysis
正解：A,B,C
質問 4：
Alibaba Cloud Content Delivery Network (CDN) is a suitable product for the following scenarios: (Number of correct answers: 2)
A. Images, HTML, CSS and JS files on a medium-sized E-commerce website.
B. News websites with more than 30 million daily page views and users are all from Singapore.
C. Static sites with more than 100,000 daily page views.
D. BBS forums with less than 100 daily page views.
正解：B,D
質問 5：
A developer recently discovered that their company's application is beginning to suffer performance degradation as a result of increased user demand for the application. After some analysis, the major bottleneck is discovered to be the RDS database instance which hosts the company's databases, "A" and "B". The developer plans to use the DTS data migration solution to move one of the databases to a new RDS instance.
Which of the following statements is correct? (Number of correct answers: 3)
A. The database account used for data migration must have read and write permissions. To ensure database security, please delete the database account used for data migration or reclaim related write permissions after data migration is completed.
B. The code for the application will have to be rewritten once this migration is complete.
C. Create a reverse data migration task and start it to migrate subsequent incremental data from target Instance database B to source instance database B.
D. After disconnecting the connection between the source instance database B and the application, you need to log in to the source database B to check the session messages to ensure that no new sessions performed write operations.
正解：A,B,D
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