Remounting a mounted file system

To remount the file system, use the TSO/E UNMOUNT command or the ISPF shell. The REMOUNT operand on the UNMOUNT command specifies that the specified file system be remounted, changing its mount mode.

Conditions under which you would remount a mounted file system are as follows:

Maintenance cannot be performed on a read-only file system. The file system must be unmounted and then mounted again as read/write. If there are cascaded mounts, all of the file systems mounted on top of that file system must also be unmounted. You can unmount and remount a root file system. However, if the file system is a shared read-only root file system in a sysplex, you must unmount the root on all other systems in the sysplex.
When you are not using shared file systems, you can use the remount facility to mount file systems as read-only under normal operating situations and as read/write to perform maintenance.

If a file is opened for a write, this is not checked if a remount operation changes the file system from read/write to read-only. Subsequent writes to the file will fail.

If a problem occurs with the remount, determine the failure, correct the problem, and try the remount again. The file system might be unavailable until the problems are corrected.