Statistics are loaded into the original database in separate rows in the system tables; they do not overwrite existing nonsimulated statistics. Simulated statistics are used only for sessions where the set statistics simulate command is in effect.
While simulated statistics are not used to optimize queries for other sessions, executing any queries by using simulated statistics may result in query plans that are suboptimal for the actual tables and indexes, and executing these queries may adversely affect other queries on the system.
