Unallocating an I/O device placeholder means disassociating it from a DeltaV I/O interface. You can unallocate an I/O device placeholder either in I/O Studio or in DeltaV Explorer.
In I/O Studio, you can unallocate an I/O device placeholder in either of the following ways:
In DeltaV Explorer, you can right-click the device placeholder or the CHARM(s) and select Unallocate Device. If you right-click the device placeholder, the CHARM(s), or the CIOC and select Delete, a dialog will appear asking if you want to unallocate the device placeholder instead of deleting it. Put a check in the checkbox if you want to unallocate instead of deleting.
An unallocated I/O device placeholder retains any configured properties and appears in Unallocated Devices in I/O Studio and DeltaV Explorer. You can see unallocated device placeholders in I/O Studio by filtering or grouping based on allocation state.
Deleting an I/O device placeholder removes the placeholder along with all its configured properties, unless the device is referenced in logic. If the device is referenced in logic and you delete the placeholder, it becomes an unassigned I/O reference.