ERROR MESAGGE:
“The database “xxx” cannot be opened. It is acting as a mirror database.”
EXPLANATION:
You experience this error if you try to perform operations such as SELECT, INSERT, UPDATE, and DELETE to the database that is acting as the Mirror in Database Mirroring in SQL Server 2005.
SOLUTION:
In Database Mirroring technology, no changes or queries can be made to the database that is in the Mirror role.
However, it can be used for reporting purposes by taking the Database Snapshot of the database that performs the Mirror task. So you can only use SELECT. You may want to read below articles.
“What is Database Snapshot On SQL Server“,
“Database Mirroring On SQL Server”