By using the SNAPSHOT isolation level during verification, you ensure the integrity of your ledger data and detect any unauthorized modifications.
The database option ALLOW_SNAPSHOT_ISOLATION must be enabled on the database before you can run the ledger verification stored procedures. The appropriate isolation level to use for the verification process is the SNAPSHOT isolation level.
When you run the database verification using the
sys.sp_verify_database_ledger_from_digest_storage stored procedure, the database must have ALLOW_SNAPSHOT_ISOLATION set to ON. This ensures that the verification process operates on a consistent snapshot of the data, preventing potential inconsistencies from concurrent transactions that might interfere with the hash computations.
The following points detail the configuration and process:
Enabling the Option: You need to use the T-SQL command ALTER DATABASE
<database_name> SET ALLOW_SNAPSHOT_ISOLATION ON; to enable this setting.
Verification Process: The verification process itself involves executing a system stored procedure that recomputes the hashes stored in the database ledger and compares them against the stored digests to detect any tampering.
Default in Azure SQL DB: Note that in Azure SQL Database, the default isolation level is READ COMMITTED SNAPSHOT ISOLATION (RCSI), which uses row versioning and has ALLOW_SNAPSHOT_ISOLATION enabled by default, so in most cases the setting is already correctly configured.
Reference:
https://learn.microsoft.com/en-us/sql/relational-databases/security/ledger/ledger-database-verification

Reference:
https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/manually-prepare-a-secondary-database-for-an-availability-group-sql-server?view=sql-server-ver15

SalesSQLDb1 experiences performance issues that are likely due to out-of-date statistics and frequent blocking queries.
A: Use sys.dm_pdw_nodes_tran_locks instead of sys.dm_tran_locks from Azure Synapse Analytics (SQL Data Warehouse) or Parallel Data Warehouse.
E: Example:
The following query will show blocking information.
SELECT
t1.resource_type,
t1.resource_database_id,
t1.resource_associated_entity_id,
t1.request_mode,
t1.request_session_id,
t2.blocking_session_id
FROM sys.dm_tran_locks as t1
INNER JOIN sys.dm_os_waiting_tasks as t2
ON t1.lock_owner_address = t2.resource_address;
Note: Depending on the system you're working with you can access these wait statistics from one of three locations:
sys.dm_os_wait_stats: for SQL Server
sys.dm_db_wait_stats: for Azure SQL Database
sys.dm_pdw_nodes_os_wait_stats: for Azure SQL Data Warehouse
Incorrect Answers:
F: sys.dm_tran_locks returns information about currently active lock manager resources in SQL Server 2019 (15.x). Each row represents a currently active request to the lock manager for a lock that has been granted or is waiting to be granted.
Instead use sys.dm_pdw_nodes_tran_locks.
Reference:
https://docs.microsoft.com/en-us/sql/relational-databases/system-dynamic-management-views/sys-dm-tran- locks-transact-sql Optimize Query Performance Question Set 2

Reference:
https://docs.microsoft.com/en-us/sql/t-sql/statements/create-table-azure-sql-data-warehouse
https://docs.microsoft.com/en-us/azure/synapse-analytics/sql/best-practices-dedicated-sql-pool

Reference:
https://rajanieshkaushikk.com/2020/09/09/how-to-choose-right-data-distribution-strategy-for-azure-synapse/