Exam AWS Certified Database - Specialty topic 1 question 106 discussion

ACD. Answer Selecting A. based on https://docs.aws.amazon.com/dms/latest/userguide/CHAP_BestPractices.html#CHAP_BestPractices.LargeTables C. and D. are the only options that have to do with increasing performance, the others are irrelevant

Correct Answer: ACF Full LOB mode – migrates all LOB data, piecewise in chunks (you provide LOB chunk size)

D can't be part of the answer. It takes about a week or more to setup a direct connect connection. I will think it ACF

https://docs.aws.amazon.com/dms/latest/userguide/CHAP_BestPractices.html B & E. Multi AZ are for improving availability should a storage issue occur, not contributing to data migration speed so B&E are out. F is opposite, "Full LOB mode provides the convenience of moving all LOB data in your tables, but the process can have a significant impact on performance." so F is out.

it should be ACF https://repost.aws/knowledge-center/dms-improve-speed-lob-data

The answer I was searching in the comments, I will post it here. For those searching for a reason to select D, and how it improves migration speed. AWS Direct Connect can reduce network costs, increase bandwidth throughput, and provide a more consistent network experience than internet-based connections

https://docs.aws.amazon.com/dms/latest/userguide/CHAP_BestPractices.html#CHAP_BestPractices.Performance

F is wrong: In full LOB mode AWS DMS migrates all LOBs from source to target regardless of size. In this configuration, AWS DMS has no information about the maximum size of LOBs to expect. Thus, LOBs are migrated one at a time, piece by piece. Full LOB mode can be quite slow. https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Tasks.LOBSupport.html

How can we break a single table into multiple DMS tasks .If the DB had multiple tables , they can be split into multiple DMS tasks . So , we cannot assume that 'large table' to mean to multiple tables. So , I will go with CDE

With Amazon RDS databases, it's a good idea to turn off backups and Multi-AZ until the cutover. So B and E eliminated F - Full LOB mode impacts performance So ACD right answer

F - Full LOB mode downgrade the performance Full LOB mode migrates all LOB data in your tables, regardless of size. Full LOB mode provides the convenience of moving all LOB data in your tables, but the process can have a significant impact on performance.

"To improve the performance when migrating a large table, break the migration into more than one task. To break the migration into multiple tasks using row filtering, use a key or a partition key" (A) A number of factors affect the performance of your AWS DMS migration: - Resource availability on the source. - The available network throughput. (D) - The resource capacity of the replication server. (C) - The ability of the target to ingest changes. - The type and distribution of source data. - The number of objects to be migrated. https://docs.aws.amazon.com/dms/latest/userguide/CHAP_BestPractices.html#CHAP_BestPractices.LargeTables

It takes much to deploy the direct connect, so D is not the correct answer. I choose ACF

B & E. Multi AZ doesn't increase speed it will add more time. F. LOB mode will ensure complete movement but not faster

https://docs.aws.amazon.com/dms/latest/userguide/CHAP_BestPractices.html#CHAP_BestPractices.LargeTables

ACF F: https://aws.amazon.com/premiumsupport/knowledge-center/dms-improve-speed-lob-data/ If you have LOBs that are larger than a few megabytes, then you can create a separate AWS DMS task with Full LOB mode. It's a best practice to create the separate task on a new replication instance to migrate these tables alone. Option A stated to create multiple DMS tasks. Having an expensive Direct Connect will not resolve this issue

Strange question. If you've already started the migration of a large table and observe that the DMS is slow it's too late for making such suggested changes. If you're planning to migrate a large table then go with A,C and D.