Problem: You are unable to change the size set parameter in the data source of an SSAS model that gets data from an Oracle database
Cause: Oracle .NET provider may not support the property you want to set
Solution: Switch to user the Oracle OLE DB Provider. It may support additional properties that are not available in the Oracle .NET provider
Using a native provider has performance advantage over a .NET provider.
From performance's standpoint, a native/OLE DB provider is more efficient than a .NET provider. We recommend to use an OLE DB Provider over an equivalent .NET provider.
In a support case, we find process times in SSAS went from 22 hours down to 2.5 hours using a remote cloud hosted Oracle data source simply by changing from the .NET Oracle provider to OLE DB Provider for Oracle