Table & still contains pooled/cluster tables (&)

What causes this issue?

You cannot change this physical table pool or table cluster whilst it
contains logical pooled tables or cluster tables. A structure change of
this type is not supported by the system.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

If you still want to change the physical table pool or table cluster,
you must start by deleting the logical tables.

Error message extract from SAP system. Copyright SAP SE.