Wrong, in most of Unix system, such as Solaris, Asynchronous I/O does not work on file systems and only on raw devices. You can enable Asynchronous I/O or configure DBWR_WRITER_PROCESSES or DBWR_IO_SLAVE to simulate Asynchronous I/O. If you use the DBWR_IO_SLAVE parameter, only one DBWR process is used, regardless of the setting of the DBWR_WRITER_PROCESSES parameter.
AIX versions 4 and higher support Asynchronous I/O (AIO) for database files created both on file system partitions and on raw devices.
Please refer to Oracle 9i R2 Administrator's Reference for Unix for more information.
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