Symptoms
Assume that you install SQL Server Data Tools (SSDT) 2017. When you try to debug a SQL Server Integration Services (SSIS) package in SSDT, the DtsDebugHost always starts in the 32-bit mode instead of the 64-bit mode.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Resolution
This issue is fixed in the following cumulative update for SQL Server:
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
Workaround
The 64-bit version of DtsDebugHost is found in the following location:
C:\Program Files\Microsoft Visual Studio 14.0\Common7\IDE\Extensions\Microsoft\SSIS\140\Binn\DtsDebugHost.exe
To work around this issue, copy the DtsDebugHost file from the VS folder to the correct location:
copy "C:\Program Files\Microsoft Visual Studio 14.0\Common7\IDE\Extensions\Microsoft\SSIS\140\Binn\DtsDebugHost.exe" "C:\Program Files\Microsoft SQL Server\140\DTS\Binn"
References
Learn about the terminology that Microsoft uses to describe software updates.