From the objective of OSS-DB Exam Silver
- Operation management - basic operation management work
Sample Question
1.39
For the VACUUM command, choose one of the most appropriate descriptions.
- Obtain the table lock of the target table and retrieve unnecessary areas in the table.
- Automatic vacuum can be executed by executing VACUUM AUTO ON.
- By executing VACUUM DETAILS, details of the execution status of VACUUM are output.
- When VACUUM ANALYZE is executed, the statistical information of the table is acquired.
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When VACUUM FULL is executed, all the tables in the database are subjected to VACUUM.
※This sample exam is different from those that appear in the actual OSS-DB Exam.
2019/05/21
Answer and Explanation
VACUUM is a command to retrieve an area in a table that is no longer necessary by updating or deleting data. If you specify the FULL option, you get an exclusive lock on the table to physically delete the unnecessary area, but by default it will not acquire the lock.
You can also execute VACUUM individually for each table, but if you do not specify the target table, all the tables in the database are targeted.
When the VERBOSE option is specified, a detailed report on the vacuum processing is output.
When the ANALYZE option is specified, statistics information of the table is acquired after the execution of the vacuum is completed.
Automatic vacuum execution is set in the setting file postgresql.conf, but it is set to run by default.
Therefore, the correct answer is D.