There is Serverless SQL Pool which queries data from files Azure Storage Account. The SQL pool is located in Central US, and Azure Storage account is located in Central India. Files are currently in Parquet format, with some files having size up to 25 GB. Which of the options tells about possible ways to increase the performance? (Multiple Choice)
 

Answer options:

A.Bring SQL pool and Azure Storage account to the same region.
B.Convert Parquet to CSV.
C.Split a large file into multiple smaller ones.
D.Enable Azure Storage throttling.

Correct Answer: A, C
Colocating Azure Storage account and serverless SQL pool is definitely increasing the network latency, which in fact plays a significant role in the performance of queries. Once they are in the same region, they will have the least network latency-related performance degradation. When you have a larger target file, the query performance will get degraded. But if you split them into smaller files, the parallel query performance can actually improve the overall total performance. There may be more than one service or application accessing the storage account which you use here.If these multiple services can add up, the IOPS requirements may reach more than the maximum network performance level of the storage account, and thus automatic throttling kicks in.
Option A is correct: Bringing SQL Pool and Azure Storage accounts to the same region can help in decreasing the latency, thus increasing the overall performance of the query.
Option B is incorrect: Parquet files have better query efficiency than CSV files. So, converting to CSV will only decrease the performance.
Option C is correct: When you have a large target file, splitting them into multiple smaller files will increase the query performance.
Option D is incorrect: There may be more than one service or application accessing the storage account which you use here. The IOPS requirements if these multiple services can add up and may reach more than the limit, azure automatically implements storage throttling. But this will make the SQL pool to run queries at a slower pace until throttling is resolved. So, this will not increase the query performance. To have better query performance, it`s better to dedicate the storage account for SQL pool only and limit other applications accessing this storage account.
Reference: To know more, please refer to the docs below: 

https://docs.microsoft.com/en-us/azure/synapse-analytics/sql/develop-best-practices#serverless-sql-pool-development-best-practices