Not all OLAP queries are for reporting. Sometimes they drive OLTP processes — really complex, separate-statements but same-transaction equivalents to "INSERT/UP

Not all OLAP queries are for reporting. Sometimes they drive OLTP processes — really complex, separate-statements but same-transaction equivalents to "INSERT/UPDATE/DELETE ... WHERE" queries. Of course, you can still drive those using a separate snapshot for the read side, to generate an ID set for a follow-up write on the business layer. But now you're doing CQRS — less trivial. You're not getting any of the ACID benefits of doing the OLAP and OLTP queries together in a single transaction; so your data model has to be designed for that (by e.g. having all tables be temporal tables.)