In my exchange 2010 environment, 4 exchange servers namely (server01, server02, server 03, server04) are in DAG.
2 DAG member servers(server01, server 02) are in primary site holding active DB copy and server03 is holding only mailbox role in primary site but not any DB copy and 1 DAG member server(server 04) is in secondary site having all passive copy of all DB.
Today I have faced issues that one of the DAG member server (server 02) in primary site were having issues and two DB were mounted in that server but suddenly I noticed that DB were become available, even I was not able to mount in another server in primary site, then also notice that exchange replication service was stopped, as soon as i started the Microsoft Exchange replication service then two affected DB automatically mounted in secondary site server04.
DAG Member : Primary Site: Server01(DB01,DB02), Server02(DB03,DB04)-active copy Server03 (only mailbox role, cas role)
Secondary site: Server04 (DB01,DB02,DB03,DB04) passive copy
Could you please advise why the two DB become mounted in secondary site. What needs to be investigated in the server to identify what actually occurred and what steps should I take to avoid this kind of incident.