Heres the scenario, I've recently come across involving a multi-instance SQL server server.
The server itself hosts a multi tiered DW, with Staging, ODS and Warehouse located in their own instance of SQL server 2008. However what happens is that Max Memory allocations are dynamically altered between each instances, depending on the state of the ETL process, so Staging->ODS the memory will be configured to favour the ODS, then during ODS->Warehouse load it will be switched to favour the Warehouse.
The Actaul DB's (ODS and Warehouse) are Very large (1-2 TB each), and as far as I'm aware the server has a total of 512GB of physical ram.
Is there a jusifitcation for doing this or would you be better leaving each instance with a fixed amount of memory?
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