From the objective of OSS-DB Exam Silver
- General Knowledge -
General Knowledge of OSS-DB
Sample Question
2.01
Choose two statements from the following that give an appropriate explanation of the PostgreSQL
tablespace.
- Improves performance by dividing up a large table and distributing it across multiple disks.
- Improves performance by placing the table and index on separate disks.
- Specifies the file name as the tablespace, and the table and index are created within that file space.
- Specifies the directory name as the tablespace, and the table and index are created as a file within that directory.
- The tablespace used by the table can only be specified when creating a new table with CREATE TABLE and cannot be modified after it is created.
※This sample exam is different from those that appear in the actual OSS-DB Exam.
2012/05/17
Answer and Explanation
Before the tablespace is created, all tables and indexes are created under the base directory of the database cluster.
The tablespace is created with CREATE TABLESPACE, and the directory used is specified as the tablespace.
The table and index are created as a file within the directory specified as the tablespace.
The tablespace used by the table can be specified as a CREATE TABLE option and modified using ALTER TABLE.
The table and index can be placed in different tablespaces. Distributing the I/O in this manner can improve performance.
Striping, where one giant database is divided across multiple disks, cannot be used with the tablespace function.
Striping via RAID, which distributes one table across multiple disks, is a realistic method for improving performance.
Therefore, the correct answers are B and D.
Other RDBMS also have the tablespace function.
They have the following in common.
The tablespace is created using CREATE TABLESPACE.
The tablespace into which the table will be placed can be specified when executing CREATE TABLE.
However, we must consider the following two questions.
Is the tablespace itself a file or a directory?
What are the benefits of using the tablespace function?
There are differences depending on the type of RDBMS used, so care should be taken.