If you use SQL Server’s Database Engine Tuning Advisor to create additional indexes, be aware that DB Upgrader needs them to be deleted before upgrading. DB Upgrader for 15.2.1 and higher drops them for you.
Note: After upgrading iMIS, you can re-add these indexes using the Database Tuning Advisor. However, iMIS gained many indexing improvements, so test performance of your upgraded system to determine whether you still need them.
If you are unsure whether tables in your database contain these statistics, run the following query:
SELECT OBJECT_NAME(s.[object_id]) AS TableName,
s.[name] AS StatName
FROM sys.stats s
WHERE OBJECTPROPERTY(s.OBJECT_ID,'IsUserTable') = 1
AND s.name LIKE '_dta_stat%';