Migrating/upgrading 20 databases from SQL Servers 2005 and 2008 R2 to 2017

  • VoldemarG

    Hall of Fame

    Points: 3482

    We are preparing for this migration, and wondering what are the worst issues and challenges we can anticipate and be prepared to resolve when migrating databases from 2008 R2 and 2005 versions to 2017 Standard edition.

    Source 2008 R2 edition is Enterprise, and source 2005 server is Standard. Is there anything on the web (we have not found much...)  like a list of worst problems to anticipate (in terms of the hardest to resolve) ?

     

    thanks.


    Voldemar
    likes to play chess

  • Grant Fritchey

    SSC Guru

    Points: 395230

    The single biggest issue you're going to hit on the database side of things is the new cardinality estimation engine that was introduced with SQL Server 2014. The new CE is great for most queries, benign for some queries, and downright evil for a few queries. The best bet to deal with this is to use the Query Store. When you migrate your databases into 2017, enable the Query Store on them, but leave them in the old compatibility mode. They'll use the old CE and performance should be largely the same (not counting bigger/faster machines,etc.). Run your load for an appropriate period of time (day, week, month, you figure it out). Then, after that period, with the data gathered by the Query Store, change the compatibility mode. If you see query regressions, you can use plan forcing to make them use the old plan until you come up with a more permanent solution (which usually entails rewriting code).

    ----------------------------------------------------
    The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood...
    Theodore Roosevelt

    The Scary DBA
    Author of: SQL Server 2017 Query Performance Tuning, 5th Edition and SQL Server Execution Plans, 3rd Edition
    Product Evangelist for Red Gate Software

  • Eirikur Eiriksson

    SSC Guru

    Points: 182321

    Grant Fritchey wrote:

    The single biggest issue you're going to hit on the database side of things is the new cardinality estimation engine that was introduced with SQL Server 2014. The new CE is great for most queries, benign for some queries, and downright evil for a few queries. The best bet to deal with this is to use the Query Store. When you migrate your databases into 2017, enable the Query Store on them, but leave them in the old compatibility mode. They'll use the old CE and performance should be largely the same (not counting bigger/faster machines,etc.). Run your load for an appropriate period of time (day, week, month, you figure it out). Then, after that period, with the data gathered by the Query Store, change the compatibility mode. If you see query regressions, you can use plan forcing to make them use the old plan until you come up with a more permanent solution (which usually entails rewriting code).

    He he, are you trying to promote your performance tuning book again Grant 🙂

    😎

    You will need to "stage" the upgrade! My advice is to use an standard instance of 2014/2016 as "staging" and restore the backups from the sources there as 2017 will not go back to 2005. You'll also have to check for enterprise functionality being used on the sources. Apart from that, this should be a walk in the park.

    I am a little surprised that you haven't found anything on the internet on this, would have thought that you should have, my first google foo turned up 31M answers .

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