Let's assuem the following scenario:
There are two sites named site A and site B. In site A, there is a LUNA. In site B, there is a LUNB. There is a remote replication between LUNA and LUNB. LUNA is primary LUN and LUNB is secondary LUN.
Database is running in site A and database needs to access LUNA. After a switch over, customer's application cannot access LUNA. The database application just corrupted with an IO error.
There are two ways to resolve this issue:
1. Do a switch over again. Make LUNA becomes primary LUN and LUNB becomes secodary LUN. Then LUNA can be accessed.
2. Delete the replication relationship between LUNA and LUNB. Then LUNA can be accessed. After application is successfully started, you can rebuild a new remote replication between LUNA and LUNB.
After switch over, LUNA becomes secondary and read-only. This causes database application cannot access LUNA with an IO error.
There should be a detailed plan before you actually perform a switch over. Primary LUN will become read-only after switch over. Make sure all applications are stopped in your primary site before switch over.