1) See database compatibility version to 120
2) index Manage depend on reorganize or rebuild index.
3) updates statistics.
4) what is memory assign in mssql ?
5) check blocking in server.
6)Check the logical and physical integrity of all the objects in the upgraded databases:
DBCC CHECKDB([myDatabase]) WITH NO_INFOMSGS
- where [mydatabase] is the database to run the integrity checks
NO_INFOMSGS option suppresses all informational messages.
If If DBCC printed any error messages you must fix them so that your database will work correctly.