Data of the tabular model will be stored in different modes called storage modes. There are two main storage modes in tabular: In-Memory and DirectQuery. The difference between these storage modes is based on the location of the stored data. In-Memory stores data in memory and DirectQuery stores data in the SQL Server database.

In-Memory is the default and recommended storage mode for the tabular model because it loads all the data into the memory and it responds to queries very quickly. Tabular models that work with In-Memory are also accessible from MDX client tools such as Excel Services. All the functionalities of DAX is supported for the In-Memory mode.

DirectQuery stores data into the SQL Server database. It is much slower than In-Memory, but as memory restrictions are much more than disk restrictions, this mode is helpful when the tabular model contains a large dataset that cannot fit into the system's memory (when you try to process the model, you may get an error if...