Mismatch between “filesystemio_options” and “disk_asynch_io”

In troubleshooting I found a setting mismatch I could use some advice on the different settings of "filesystemio_options” and “disk_asynch_io”.

I am confused on how these values are affecting each other. We are a non-rac,  Release 11.2.0.2.0, database for APPS R12.1.3 .

Our parameter for “filesystemio_options” value is “SETALL”.

SETALL- Enables both direct I/O and asynchronous I/O where possible.

I also found that the “disk_asynch_io” value is “FALSE”.

Would this mean that our database is not utilizing asynchronous I/O?

I note in Oracle Database Reference 11g Release 1 (11.1):

“If you set DISK_ASYNCH_IO to false, then you should also set DBWR_IO_SLAVES to a value other than its default of zero in order to simulate asynchronous I/O.”