How to setup async IO (aio)

Configuring aio

1. create the /dev/async character device

# /sbin/mknod /dev/async c 101 0x0
# chown oracle:dba /dev/async
# chmod 660 /dev/async

2. configure the async driver in the kernel:

# kcmodule asyncdsk=static

this will require a kernel rebuild and reboot.

3. set max_async_ports:

# kctune max_async_ports=<value>

max_async_ports limits the maximum number of processes that can concurrently use /dev/async. Set this parameter to the sum of ‘processes’ from init.ora + number of background processes. The background processes started at instance startup will open /dev/async twice.

If max_async_ports is reached, subsequent processes will use synchronous I/O

How to check # ports in use:

# fuser -u /dev/async 2>/dev/null | wc -w
103