A company has been using Amazon Redshift and loaded a number of tables in the cluster. After a series of operations over a couple of months, the performance of the queries seems to be deteriorating. Which of the following is an ideal approach to improve the performance of the queries?

Answer options:

A.Carry out the VACUUM command
B.Carry out the COPY command on the table again
C.Enable compression on the columns
D.Disable compression on the columns

Answer – A
The AWS Documentation mentions the following
Amazon Redshift does not automatically reclaim and reuse space that is freed when you delete rows and update rows. To perform an update, Amazon Redshift deletes the original row and appends the updated row, so every update is effectively a delete followed by an insert. When you perform a delete, the rows are marked for deletion, but not removed. The query processor needs to scan the deleted rows as well as undeleted rows, so too many deleted rows can cost unnecessary processing. You should vacuum following a significant number of deletes or updates to reclaim space and improve query performance.
Option B is incorrect since you will first need to get the latest data and then perform the COPY command. And why do this when you can use the VACCUM command to improve performance
Option C is incorrect since this is done when the table is created
Option D is incorrect since this is do with the size and not the performance of queries
For more information on reclaiming storage in Redshift, please refer to the below URL
https://docs.aws.amazon.com/redshift/latest/dg/t_Reclaiming_storage_space202.html