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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
Hi @Stefan , did below answers could help you? If there have any answers helped you, please do "Accept Answer". By doing so, it will benefit for community members who have this similar issue. Your contribution is highly appreciated. Thank you!
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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Thanks for your answer.
I have not find much to read about the "Online attach" feature. Just this short announchment (What's New in SQL Server Analysis Services 2019) on the link you provided.
Is there anymore information on this?
You wrote:
After synchronization finishes, Analysis Services automatically switches the users to the newly copied data and metadata, and drops the old data
Are you reffering to "online attach" when you wrote this? Bit confused since you are talking about "synchronization".
Regards
Stefan
Hi @Stefan , based on my research, Online attach is a new feature, I also did not find too much related documents. For the second question, I quoted it from the second link which I provided before. Because you are talking about 'built-in SSAS Synchronization', I think you need some information about that. Sorry for making you confused. If you did not needed, please ignore it.
Hi again,
No problem.
I´m using synchronization today, so the questions was mostly around online attach and if that could be better than synchronization in my scenario.
So based on that, and my first question; "if I will get the same problem using online attach (as I get with Synchronization) around new queries getting blocked and old queries being aborted. Do you know a sure answer on that based on the thin documentation available?