The Oracle database server uses an AIX applet, and the small machine is a one-level mount point issue for NFS client use

It is important to master a knowledge point:

In Aix operating system (only Aix has this problem, other OS does not have this problem), if this AIX small machine is used as NFS client, and this small machine is also Oracle database server, and on this small machine df-g see the mount point (for example,/rman) is a level of directory, If there is a problem with NFS (including an NFS server outage, a disconnect between NFS client and NFS server, and so on), an exception occurs on the Oracle database on the NFS client (this is the small machine that is the Oracle database server): the instance freezes, the new connection Connection cannot be connected.

Therefore, when using NFS, be sure to use a level two directory as a mount point (such as/rman/backup)

If the AIX that is running is already on the top (as an NFS client, with a first-level mount point and NFS problems), what happens? The only way to do this is to restart the Aix machine, or the Oracle database on the AIX applet will not be able to provide external services.

Reference Articles for:
Disconnected NFS Mount Point causes Instance to hang on AIX (Doc ID 1445600.1)

When NFS server was down, the Oracle server freezes with No Errors in Alert Log File (Doc ID 1316251.1)

The Oracle database server uses an AIX applet, and the small machine is a one-level mount point issue for NFS client use