Scale-out Synchronize or Online Attach

Stefan 191 Reputation points
2021-07-05T14:19:08.21+00:00

Hi,

I´ve a SSAS Tabular environment with one dedicated server for "Processing" and another server handling the user query-load.
The SSAS database is processed (only some partitions) multiple times per day (around ones per hour) and the "delta" is "copied" to the query server using the built-in SSAS Synchronization.
One problem that we have is that the query server usualy gets inaccessible for some time (stopes accepting new queries) in the late phase of the synchronization (I think it is when it is switching to new version of the database). Feels like 1-2 minutes or something, but it propably varies. I also think (not sure) that the time of the synchronization (or final commit) vary depending on query load (synch takes longer time because it waits for queries to complete before commiting the synch).

Cause of this I have been starting to think about the new "online attach" feature in SSAS 2019. Will that one behave different on a highly concurrent environment?
Will it be more like 2 "separate" databases on different versions so that an already running query will be able to complete on the the old version and the new version starts accepting new queries or will I get the same problem with the "Online attach" approach?

Regards
Stefan

SQL Server Analysis Services
SQL Server Analysis Services
A Microsoft online analytical data engine used in decision support and business analytics, providing the analytical data for business reports and client applications such as Power BI, Excel, Reporting Services reports, and other data visualization tools.
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  1. CarrinWu-MSFT 6,866 Reputation points
    2021-07-06T03:39:15.667+00:00

    Hi @Stefan ,

    Welcome to Microsoft Q&A!

    will I get the same problem with the "Online attach" approach?

    Yes, you will. Online attach may require double the model memory to keep the old version online while loading the new version. After synchronization finishes, Analysis Services automatically switches the users to the newly copied data and metadata, and drops the old data from the destination database. Please refer to Online attach and Synchronize Analysis Services Databases to get more details.

    Best regards,
    Carrin


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