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Oracle® Database Reference 10g Release 2 (10.2) Part Number B14237-02 |
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# DBWR_IO_SLAVES

Property | Description
--- | ---
Parameter type | Integer
Default value | `0`
Modifiable | No
Range of values | 0 to operating system-dependent
Basic | No

`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 nonzero value, the number of I/O server processes used by the `ARCH` and `LGWR` processes is set to `4`. However, the number of I/O server processes used by Recovery Manager is set to `4` only if asynchronous I/O is disabled (either your platform does not support asynchronous I/O or `disk_asynch_io` is set to `false`).

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"