There is a Dedicated SQL Pool in which the existing tables are using clustered columnstore index. You are planning for partition splitting to improve the performance following your partition strategy. You run the ALTER function on the first two tables, but they were not successful. Which of the options tells about the possible reasons for this failure? (Multiple choice)
 

Answer options:

A.Clustered columnstore containing data cannot be partition splitted.
B.Partition which is getting splitted should be empty while using ALTER statement.
C.Clustered columnstore index with data can be splitted using CTAS statement only.
D.The entire table must be empty before running partition splitting in case of clustered columnstore index.

Correct Answer: A and B
There are certain limitations while using ALTER PARTITION STATEMENT for partition splitting of the table that already has data and using clustered columnstore indexing. 
You will see the following ERROR: 
“ALTER PARTITION statement failed because the partition is not empty. Only empty partitions can be split in when a columnstore index exists on the table. Consider disabling the columnstore index before issuing the ALTER PARTITION statement; then rebuilding the columnstore index after ALTER PARTITION is complete.” 
The partition split will need the specific partition to be empty. It is not mandatory that the whole table should be empty. Also, in the case of clustered columnstore, the CTAS may not work if you have data in the partition. Options A and B are correct: Clustered columnstore containing data cannot be partition split. Also, if a Partition contains data, the data should be split first. But this works only if your table is not using clustered columnstore indexing.
Options C and Dare incorrect: Even if CTAS statement is used, it will be failing since the scenario tells that the tables are columnstore indexed. But they are not a mandatory rule that the entire table must be empty for partition splitting.
Reference: To know more, please refer to the document below: 

https://docs.microsoft.com/en-us/azure/synapse-analytics/sql-data-warehouse/sql-data-warehouse-tables-partition#partition-switching