Can database administrators change physical schema? I was reading the Chapter 1 of the 7th edition of Database System Concepts and ran into this:

• Schema and physical-organization modification. The DBA carries
out changes to the schema and physical organization to reflect the
changing needs of the organization, or to alter the physical
organization to improve performance.

Is it true that database administrators can access the physical schema and change it or have I misunderstood what is cited above?
One of the innovation of the relational model was to separate thr logical view that programmers see (tables of columns) from the physical storage (files on disks). To function the DBMS must be aware of both and hence must have the ability to amend both. So yes, if you define DBA as &quot;someone who manages a DBMS&quot; a DBA can change the physical schema.
Most DBMS implement a permission system. Different permissions will affect the creation of tables and the use of disks. In smaller teams it may be that one person has granted both of these permissions. In larger teams it becomes more likely the tasks are separated. You will find application DBAs defining tables and queries and operational DBAs looking after disks and CPUs. In businesses dealing with financial data or PII it may be that neither of those roles has access to any of the data.