A method comprising: receiving a data query from a tenant assigned to a first virtual data warehouse within a multi-tenancy data warehouse , wherein the multitenancy data warehouse at least includes the first virtual data warehouse and a second virtual data warehouse , wherein the first virtual data warehouse is a database that is part of a first physical data centre; generating a set of information, based on the data query, indicating data the tenant is authorized to access within the multi-tenancy data warehouse ; receiving a declaration from the tenant to utilize a subset of the data which the tenant can access as indicated by the set of information; determining, by a replica management module , whether the subset of the data is in a second physical data centre that is different to the first physical data centre; in response to determining the subset of the data is in a second physical data centre from the first physical data centre, caching, by a transfer control module , the subset of the data from the second physical data center in the first physical data center; importing, into the first virtual data warehouse, data that is outside of the first virtual data warehouse using a link identifying a set of parameters for retrieving the data, the set of parameters comprising a time range; creating, by a retention management module , a retention virtual warehouse associated with a retention policy, creating, by a linking module , links to data that needs to be maintained under the retention policy; monitoring, by a garbage collection module , the use of the link; and updating, by the garbage collection module , the time range to a smaller time range based on the current use of the retrieved data. receiving a data query from a tenant assigned to a first virtual data warehouse within a multi-tenancy data warehouse , wherein the multitenancy data warehouse at least includes the first virtual data warehouse and a second virtual data warehouse , wherein the first virtual data warehouse is a database that is part of a first physical data centre; generating a set of information, based on the data query, indicating data the tenant is authorized to access within the multi-tenancy data warehouse ; receiving a declaration from the tenant to utilize a subset of the data which the tenant can access as indicated by the set of information; determining, by a replica management module , whether the subset of the data is in a second physical data centre that is different to the first physical data centre; in response to determining the subset of the data is in a second physical data centre from the first physical data centre, caching, by a transfer control module , the subset of the data from the second physical data center in the first physical data center; importing, into the first virtual data warehouse, data that is outside of the first virtual data warehouse using a link identifying a set of parameters for retrieving the data, the set of parameters comprising a time range; creating, by a retention management module , a retention virtual warehouse associated with a retention policy, creating, by a linking module , links to data that needs to be maintained under the retention policy; monitoring, by a garbage collection module , the use of the link; and updating, by the garbage collection module , the time range to a smaller time range based on the current use of the retrieved data. <EOS>