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DISK_ASYNCH_IO

DISK_ASYNCH_IO controls whether I/O to datafiles, control files, and logfiles is asynchronous (that is, whether parallel server processes can overlap I/O requests with CPU processing during table scans).  If your platform supports asynchronous I/O to disk, Oracle recommends that you leave this parameter set to its default value. However, if the asynchronous I/O implementation is not stable, you can set this parameter to false to disable asynchronous I/O. If your platform does not support asynchronous I/O to disk, this parameter has no effect.

  • For optimum performance make sure you use asynchronous I/Os.
  • TRUE is the default parameter value for the majority of platforms.

SQL>SHOW PARAMETER disk_asynch_io
NAME TYPE VALUE
------------------------------------ ----------- ------
disk_asynch_io boolean TRUE
SELECT * FROM v$parameter WHERE lower(name) = 'disk_asynch_io' ;

These parameters enable or disable the operating system’s asynchronous I/O facility. They allow query server processes to overlap I/O requests with processing when performing table scans.

Asynchronous operations are currently supported for parallel table scans, hash joins, sorts, and serial table scans. However, this feature can require operating system specific configuration and may not be supported on all platforms.

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