mvfs | Build and install mvfs module

I have provided migration advice from ClearCase to Git before, but the TLDR; remains:

• Keep ClearCase in read-only for archive
• Take a snapshot of the latest code, and create a Git repository in it, modifiy its .gitignore (in order to not add everything), add a remote and push to a Git repository hosting server.

That is:

First, you need to be root.

Stop all Clearcase services on AIX system - Stop completly Clearcase

Second, the official documentation init_ccase does mention, in addition of /etc/rc.atria { start | stop }:

• Unexports any view/VOB combinations that were exported through /etc/exports.mvfs to enable non-ClearCase access
• Unmounts all VOBs
• Kills the vob_server processes for VOBs whose storage directories are on the local host
• Kills the albd_server process, which also causes view_server, db_server, and vobrpc_server processes to exit
• Kills the lockmgr process
• (On AIX 4) Unloads the MVFS from the operating system kernel
• Unmounts the viewroot directory

So regarding MVFS and AIX 4, the "Loading and Unloading Kernel Extensions" page suggests kmod_unload command.

That would stop completely ClearCase.

The commands listed in "Uninstall ClearCase 7.1 on Linux or Unix" (section AIX), like rmvfs mvfs, would be "too much" here.

I'm trying not to have to rely on the Err object, i.e. not use a cleartool command that fails when it encounters a non-existing version (such as get or descr).

That is precisely what you should rely on, unless you have constraint (like testing thousands of elements per second, or other performance bottleneck)

cleartool describe can be applied on an extended pathname and will fail if it does not exist.

As commented by Brian Cowan, you can check if Excel VBA can call commands from the ClearCase Automation Library (CAL).
I have used CAL in VB Script before.