Allianz Financial Services (AFS) is a banking group offering end-to-end banking and financial solutions in South East Asia through its consumer banking, business banking, Islamic banking, investment finance and stock broking businesses as well as unit trust and asset administration, having served the financial community over the past five decades.
AFS uses Redshift on AWS to fulfill the data warehousing needs and uses S3 as the staging area to host files. AFS uses other services like DynamoDB, Aurora, and Amazon RDS on remote hosts to fulfill other needs. The team uses load the data from different data sources using COPY command. What are the best practices to load using COPY command to copy the data from S3? select 3 options.

Answer options:

A.Split your data into multiple files and upload to S3
B.Run a single COPY command to load the table.
C.multiple concurrent COPY commands to load one table from multiple files resulting in parallel load
D.use VACUUM process at the end of the load, if the table has a sort column defined

Answer : A,B,D
Option A is correct -The COPY command leverages the Amazon Redshift massively parallel processing (MPP) architecture to read and load data in parallel from files in an Amazon S3 bucket. You can take maximum advantage of parallel processing by splitting your data into multiple files and by setting distribution keys on your tables 
https://docs.aws.amazon.com/redshift/latest/dg/t_Loading-data-from-S3.html
Option B is correct -Amazon Redshift automatically loads in parallel from multiple data files.
If you use multiple concurrent COPY commands to load one table from multiple files, Amazon Redshift is forced to perform a serialized load. This type of load is much slower and requires a VACUUM process at the end if the table has a sort column defined 
https://docs.aws.amazon.com/redshift/latest/dg/c_best-practices-single-copy-command.html
Option C is incorrect -Amazon Redshift automatically loads in parallel from multiple data files.
If you use multiple concurrent COPY commands to load one table from multiple files, Amazon Redshift is forced to perform a serialized load. This type of load is much slower and requires a VACUUM process at the end if the table has a sort column defined 
https://docs.aws.amazon.com/redshift/latest/dg/c_best-practices-single-copy-command.html
Option D is correct -Amazon Redshift automatically loads in parallel from multiple data files.
If you use multiple concurrent COPY commands to load one table from multiple files, Amazon Redshift is forced to perform a serialized load. This type of load is much slower and requires a VACUUM process at the end if the table has a sort column defined 
https://docs.aws.amazon.com/redshift/latest/dg/c_best-practices-single-copy-command.html