Enable Compatibility Level 120 and Trace Flag 4199

Add Trace Flag 4199 as a Startup Parameter

Trace flag 4199 must be enabled each time the server is started, unless it is added as a startup parameter. For self-hosted clients, this can be enabled on startup by adding "-T4199" as a start-up parameter in SQL Server Configuration Manager. Once the startup parameter is added, restart SQL Server to enable trace flag 4199.

1. In SQL Server Configuration Manager, in the Configuration manager pane, click SQL Server Services.
2. Right-click the server from the list and click Properties.
3. In the Properties dialog, select the Startup Parameters tab.
4. In the Specify a startup parameter field, enter -T4199 and click Add. 
5. Click OK.

Note: Trace flag 4199 will be enabled globally (affecting all databases on the instance). Any other user databases on the system at compatibility level 120 will have the query optimizer hotfixes enabled.

For more information refer to: https://support.microsoft.com/en-us/help/974006/sql-server-query-optimizer-hotfix-trace-flag-4199-servicing-model

Set the Database Compatibility Level to 120

To set the database compatibility level to 120 while following best practice guidelines, the database must first be set to single-user mode to disconnect any active sessions before the compatibility level is changed. This process avoids generating incorrect query plans based on multiple compatibility levels. Execute the following query on the database in SQL Server Management Studio:

Note: It does not need to be re-run on startup.

ALTER DATABASE evolv_database_name SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
ALTER DATABASE evolv_database_name SET COMPATIBILITY_LEVEL = 120;
ALTER DATABASE evolv_database_name SET MULTI_USER;

For more information refer to: https://docs.microsoft.com/en-us/sql/t-sql/statements/alter-database-transact-sql-compatibility-level

Validate

To validate that the database is at compatibility level 120, either check in the Database Properties - Options page in SQL Server Management Studio or run the following query and ensure the result is 120:

SELECT compatibility_level FROM sys.databases WHERE name = 'evolv_database_name'

For optimal performance, you must operate compatibility level 120 with trace flag 4199 enabled. To verify that trace flag 4199 is enabled, run the following query:

DBCC TRACESTATUS(4199) 

To determine the version of SQL Server installed, run the following query in SQL Server Management Studio:

SELECT SERVERPROPERTY('productversion')

Evolv is supported at database compatibility level 120 when SQL Server 2014 is at service pack 1 or greater (product version 12.0.4100.1). Refer to https://support.microsoft.com/en-us/help/321185/how-to-determine-the-version--edition-and-update-level-of-sql-server-a#completeversion to determine the version name, service pack, and update level based on the product version number.