Opens all database files (the main database file, dbspaces, transaction log, and transaction log mirrors) as read-only, with
the exception of the temporary file, when the option is specified before any database names on the command line. No changes
to the database(s) are allowed: the database server does not modify the database file(s) and transaction log files.
If the -r option is specified after a database file, only that specific database is read-only. You can make changes on temporary
tables, but ROLLBACK has no effect, since the transaction and rollback logs are disabled.
A database distributed on a CD-ROM device is an example of a database file that cannot be modified. You can use read-only
mode to access this sort of database.
If you attempt to modify the database, for example with an INSERT or DELETE statement, a SQLSTATE_READ_ONLY_DATABASE error
Databases that require recovery cannot be started in read-only mode. For example, database files created using an online backup
cannot be started in read-only mode if there were any open transactions when the backup was started, since these transactions
would require recovery when the backup copy is started.
You cannot start a database in read-only mode if auditing is turned on.