Hello @Abhijeet Kumar , Thanks for the question and using MS Q&A platform.
While deciding the Tier, you should also consider the calculation which you are going to perform on the records. Let's say that if you are creating a formula on a column on all the 99 million, it will take up the compute and should be factored in. I doubt if S0 will suffice the ask as it only have 10 GB of memory, I think you can start with that and then Scale up. You can scale-up or down in the same tier from the portal.
https://learn.microsoft.com/en-us/azure/analysis-services/analysis-services-overview#standard-tier
Himanshu
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