Initialization Parameters, 42 of 188

DBWR_IO_SLAVES

Parameter type:	Integer
Parameter class:	Static
Default value:	0
Range of values:	0 to operating system dependent value
`DBWR_IO_SLAVES` is relevant only on systems with only one database writer process (`DBW0`). It specifies the number of I/O server processes used by the `DBW0` process. The `DBW0` process and its server processes always write to disk. By default, the value is 0 and I/O server processes are not used. If you set `DBWR_IO_SLAVES` to a non-zero value, the numbers of I/O server processes used by the `ARCH` process, `LGWR` process, and Recovery Manager are set to 4.
Typically, I/O server processes are used to simulate asynchronous I/O on platforms that do not support asynchronous I/O or that implement it inefficiently. However, you can use I/O server processes even when asynchronous I/O is being used. In that case the I/O server processes will use asynchronous I/O. I/O server processes are also useful in database environments with very large I/O throughput, even if asynchronous I/O is enabled. See Also: "BACKUP_TAPE_IO_SLAVES".