At least one installed device exists for device category &1

What causes this issue?

The action is not possible as at least one installed device or a device
info record exists for device category &V1&.

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

IF &[SWITCH]ISU_AMI_EHP5& = 'X'.
You cannot change the <LS>Advanced Meter</> field from "2" (<LS>Advanced
Meter</>) or "3" (<LS>Advanced Meter Capability via AMI Device</>) to
any other value.
ELSE
You cannot change the <LS>Advanced Meter</> field from "2" (<LS>Advanced
Meter</>) to any other value.
ENDIF
You cannot delete the following data:
Determination group of advanced metering system
Determination group of advanced meter capability group

System Response

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.