Steps for dynamically replacing the sysplex root file system

About this task

Before you begin: You need to ensure that the following requirements have been met:

All systems in the sysplex are at the V1R10 or later level.
The current sysplex root PFS, and the new sysplex root PFS, are up in all the systems in shared file system configuration.

Also, be aware of the following restrictions:

The sysplex root must be locally mounted on all systems in the shared file system configuration.
Byte range locks must not be held on the sysplex root during replacement processing.
The current sysplex root and the new sysplex root must be either HFS or zFS in any combination.
The sysplex root or any directories on it cannot be exported by the DFS or SMB server.

Note the following facts:

Remote NFS mounts of the sysplex root or any directories on it are considered active use of the current sysplex root file system.
During the replacement, the new sysplex root must not be HSM-migrated, mounted, or in use.
Mount parameters are preserved during the replacement of the sysplex root of the same file system type (PFS). They are dropped if the file system type is different.
Directories, data, files, and links are not copied from one file system to another.

Perform the replacement as follows:

To verify that the sysplex root is locally mounted on all systems, issue:
```
Ro *all, D OMVS,F,NAME=root_file_system_name
```
You should see CLIENT=N for each system.
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Allocate a new file system to be used as the new sysplex root file system.
When allocating new file systems, follow these rules:
- The UID, GID, and the permission bits of the root directory in the new sysplex root file system must match those of the root directory in the current sysplex root file system.
- If the SECLABEL class is active and the MLFSOBJ option is active, then the multilevel security label for the new sysplex root must be identical to the assumed multilevel security label of the current sysplex root.
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On the new sysplex root, set up the mount points and the symbolic links. The mount points and the symbolic links must be same as the ones on the current sysplex root.
1. Mount the new sysplex root file system at a temporary mount point (for example, /newroot).
2. Verify that all systems in the shared file system configuration have direct access to the new sysplex root file system and can locally mount it. Issue
```
Ro *all, D OMVS,F,NAME=new_sysplex_root_file_system_name 
```
  and verify that CLIENT=N for each system.
3. Select one of the following recommended ways to set up mount points and symbolic links:
  - Use the pax shell command to populate the new sysplex root file, using the current sysplex root as a source. For example:
```
cd /
pax -wr -pe -XCM ./ /newroot
```
  - Use copytree to populate the new sysplex root, using the current sysplex root as a source. For example:
```
copytree -as / /altroot
```
  - Manually issue mkdir and ln -s shell commands to create the mount point directories and symbolic links similar to the current sysplex root.
4. Unmount the new sysplex root.
_______________________________________________________________
On any system in the shared file system configuration, issue:
```
F OMVS,NEWROOT=new.root.file.system.name,COND=<YES|NO|FORCE>
```
YES

Proceed conditionally. The system checks for active usage in the current sysplex root file system and reports the active usage in a BPXF245I message. If file activity is found, the command fails with EBUSY return code and JrActivityFound reason code; message BPXF244E is also displayed. If file activity is not found, the command continues processing to replace the sysplex root. YES is the default.

NO

Proceed unconditionally. The system checks for active usage in the current sysplex root and reports the active usage in a BPXF245I message. Replacement of the sysplex root continues.

FORCE
Forces the replacement of the current sysplex root with the new sysplex root. This option allows user to replace a failing sysplex root with the user-specified new sysplex root.
A BPXI085D WTOR message is issued to the console to confirm the FORCE option. Mount points are validated. Symbolic links are not validated.
In addition to the restrictions listed Steps for dynamically replacing the sysplex root file system, these restrictions must be met in order to use the FORCE option:
- All systems in the sysplex must be at the V1R11 or later level.
- The real path name for the mount points in the current sysplex root must not exceed 64 characters in length.
The replacement of the sysplex root file system begins. During the replacement, active connections to files and directories in the current sysplex root file system are broken.

After the replacement completes:
- The root (/) is updated on all systems in the sysplex to point to the new sysplex root file system.
- New opens go to the new sysplex root file system. The current sysplex root for the root directory is replaced for all processes in all systems. The current directory for root directory is replaced for any processes that use it.
- Old connections in the previous sysplex root file system might get EIO errors.
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Update the TYPE parameter and name of the sysplex root file system in the BPXPRMxx member of SYS1.PARMLIB.

When you are done, you have dynamically replaced the sysplex root file system.