You can disable this Concurrent IO option by using smitty jfs2, go to change /show ... locate your file systems and remove the cio from Mount options. You can also edit the /etc/filesystems by hand to remove this option from the stanza in question. Remount of /oracledata is required for changes to take effect.

The only problem here is Oracle performance. By using cio option on the mountpoint the databases performance is greatly increased. If you choose to change this configuration you migth want to look in to tuning vmo parameters to decrease the degree of file system buffers used by the system.