SQL 2019 AG and system databases

  • tony28

    SSCertifiable

    Points: 7068

    Hello,

    I read that in new SQL is Ag feature also for sync system database, can you give me some hint please ?

    I cannot find how to set.

    thanks



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  • Sue_H

    SSC Guru

    Points: 90588

    tony28 wrote:

    Hello,

    I read that in new SQL is Ag feature also for sync system database, can you give me some hint please ?

    I cannot find how to set.

    thanks

    Here is a link to the latest database requirements with SQL Server 2019 Availability Groups:

    Prerequisites, Restrictions, and Recommendations for Always On availability groups

    And the first one in the list is:

    Be a user database. System databases cannot belong to an availability group.

    Sue

     

  • tony28

    SSCertifiable

    Points: 7068

    Hi,

    ah I see something like this, but everywhere they presented that is new feature also for system dbs, so it looks like wasnt released .

     

    thanks for info



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  • Grant Fritchey

    SSC Guru

    Points: 396384

    tony28 wrote:

    Hi,

    ah I see something like this, but everywhere they presented that is new feature also for system dbs, so it looks like wasnt released .

    thanks for info

    I can't imagine that would be the case. Let's just think about it for a second. Availability Groups work on moving around individual databases with a shared-nothing process. This means that DatabaseA can exist on two servers. But, on one server is DatabaseB and on the other server is DatabaseC. If you move the master database from the first server, what happens to DatabaseC? If you could, can you show a link to what was telling that they're now supporting system databases in AG?

    ----------------------------------------------------
    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

  • Jeffrey Williams

    SSC Guru

    Points: 88324

    From what I have read - SQL Server 2019 includes support for 'Big Data Clusters'.  If you setup and configure this (https://docs.microsoft.com/en-us/sql/big-data-cluster/deployment-high-availability?view=sql-server-ver15) then the system databases are automatically included.

     

    Jeffrey Williams
    Problems are opportunities brilliantly disguised as insurmountable obstacles.

    How to post questions to get better answers faster
    Managing Transaction Logs

  • Grant Fritchey

    SSC Guru

    Points: 396384

    Ah, the big data clusters. Those are wicked cool. Also, they're not Availability Group technology. Well, I'm sure some is utilized. However, it's not a traditional AG. Instead, that's a large set of containers managed through Kubernetes. This is utterly different from AG. It's not an availability group, with one database getting all the reads, then transactions replicated across to one or more secondaries, which are readable, and a failover capability. Instead, it's a whole slew of containers, masquerading as a single database, with writes going on all over the place, not one location, but hundreds. It's just a different animal not to be construed with, what is now, old fashioned AG.

    ----------------------------------------------------
    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

  • Jeffrey Williams

    SSC Guru

    Points: 88324

    I think the confusion is that the documentation references availability groups - specifically in relation to high availability mode.  By default, if that setting is enabled then the containedag availability group is created and all user and system databases are automatically included in the contained availability group.

    It does look wicked...

    With that said - I still much prefer the old VMS (DEC) clusters running DSM (or Intersystems Cache).  Fully load balanced cluster with a single database system across all nodes in the cluster.

    Jeffrey Williams
    Problems are opportunities brilliantly disguised as insurmountable obstacles.

    How to post questions to get better answers faster
    Managing Transaction Logs

  • tony28

    SSCertifiable

    Points: 7068

    Grant Fritchey wrote:

    tony28 wrote:

    Hi,

    ah I see something like this, but everywhere they presented that is new feature also for system dbs, so it looks like wasnt released .

    thanks for info

    I can't imagine that would be the case. Let's just think about it for a second. Availability Groups work on moving around individual databases with a shared-nothing process. This means that DatabaseA can exist on two servers. But, on one server is DatabaseB and on the other server is DatabaseC. If you move the master database from the first server, what happens to DatabaseC? If you could, can you show a link to what was telling that they're now supporting system databases in AG?

     

    Hi.

    I understand, also for me it was little suprise how can works, because directly like you told

    But on SQL Bits and also on some another news before released 2019 was about AG with system dbs.

    Maybe it was wrong understanding you know and it wasnt directly on AG.

    Thanks 🙂

    • This reply was modified 1 month ago by  tony28.
    • This reply was modified 1 month ago by  tony28.



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  • Ben Miller

    SSCrazy

    Points: 2964

    It is a feature of the Big Data Cluster part of the SQL 2019 Release. It did not make it into the Relational Engine this release. So no system dbs in an AG.



    Ben Miller
    Microsoft Certified Master: SQL Server, SQL MVP
    @DBAduck - http://dbaduck.com

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