※This sample exam is different from those that appear in the actual OSS-DB Exam.
There are two ways to back up the database: a method of physical backup that physically copies the files that make up the database, and a method of logical backup that logically copies the contents of the database in the form of SQL.
Commands such as pg_dump and pg_dumpall are prepared for logical backup.
Physical backups are done using OS commands such as tar. At this time you need to stop the database.
Physical backups are the directories of the database cluster, but if you are using the table space functionality, you also need to create a copy of the files in the directory in the tablespace at the same time.
It is mainly the data of the table that constitutes the logical backup. Physical backups include those that are not included in logical backups, such as indexes, so in general physical backups are larger in size.
Therefore, the correct answers are A and C.