DISK_ASYNCH_IO

Property	Description
Parameter type	Boolean
Default value	true
Modifiable	No
Range of values	true | false
Basic	No

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.

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.

Note:

1. Related parameter: DBWR_IO_SLAVES, ASYNC_READ (Oracle 7)

2. This parameter is introduced in Oracle 8.0. It replaces various port specific parameters for ASYNCHRONOUS IO in Oracle 7 (eg: ASYNC_READ). If DISK_ASYNCH_IO is set to FALSE, then typically either DBWR_IO_SLAVES DB_WRITER_PROCESSES should be set unless the system is low throughput.

3. Query for the current value of the parameter

select name, value, isdefault, isses_modifiable, issys_modifiable,

isinstance_modifiable, isdeprecated, description

from v$parameter where upper(name) = ‘DISK_ASYNCH_IO’;

NAME	VALUE	IS DEFAULT	ISSES_ MODIFIABLE	ISSYS_ MODIFIABLE	ISINSTANCE_ MODIFIABLE	IS DEPRECATED	DESCRIPTION
disk_asynch_io	TRUE	TRUE	FALSE	FALSE	FALSE	FALSE	Use asynch I/O for random access devices

Oracle initializatoin parameters