SQL DBA data type is changed after upgrade
You should perform the following tasks after updating :


Upgrade Database Compatibility Level


The database compatibility level needs to be manually changed on the 2014 instance

Run DBCC CHECKDB WITH DATA_PURITY


Checks for invalid data values based on column data type

Run DBCC UPDATEUSAGE


Corrects page count inaccuracies to reflect accurate information when using sp_spaceused

Run sp_refreshview


Ensures that views are up to date

Update Statistics


Brings database statistics are up to date to allow the query optimizer to choose the best query plan

Take a Full Backup of the Database
Make sure you can recover the database with all of the migration efforts
Monitor Performance between Cardinality Estimators


It’s important to note: SQL Server 2014 received a major overhaul of the cardinality estimator. For the vast majority of queries, performance will improve due to better row estimations. However, in some scenarios estimations could be worse which may result in performance degradation. It’s important to monitor most commonly used queries to see if any performance degradation is resulting from poor estimations. It is possible to utilize the old cardinality estimator by leveraging a database compatibility level of 110 or lower or by leveraging trace flag 9481.