Check for physical indexes with no assignment to logical index (InfoCube)

What causes this issue?

This check searches for physical indexes that are not assigned to
logical indexes or index joins and are therefore no longer available for
executing BEx queries. Logical indexes or index joins correspond to BW
InfoProviders.
When an InfoProvider is deleted from the SAP NetWeaver BW Accelerator,
some physical indexes of this kind of index join may not be fully
deleted and may remain on the hard disk.
The details for the check provide additional information and list the
names of the indexes that are no longer assigned.

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?

Delete those indexes identified by the check that are no longer assigned
to logical indexes. Contact your system administrator for more
information.
If the system proposes a solution, implement it by following the
instructions.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.