You cannot initialize these databases asynchronously, even if you explicitly use the async_init parameter:
All system databases
All temporary databases, system or user
Archive databases
Proxy databases
Any database created with the for load option
These commands cannot be run in a database that it still undergoing initialization:
unmount database
alter database ... log off
You can put the database into single user mode during initialization. However, the initializer does not run while the database is in single user mode, and is automatically restarted to continue initialization when you take the database out of single user mode.
You may notice a slight performance impact to DMLs that
use the space in the database being initialized while the asynchronous
initialization service task is running.
