Updating an Existing List Entry

When you update an existing list entry (ENTRYTYPE=OLD) or might do so (ENTRYTYPE=ANY), you can designate the target list entry in several ways:

To specify the head or tail entry on a particular list, code the list position (LISTPOS) and the list number (LISTNUM).
To specify a particular entry regardless of where it resides in the list structure, code one of the following:
- The entry name (ENTRYNAME), for named entries only.
- The entry ID (ENTRYID).
You can code the LISTNUM parameter to stipulate that the selected entry must reside on a certain list.
To specify a keyed list entry at the head or tail of a sublist of list entries with the same key, code the list entry's key (ENTRYKEY), the position on the sublist (LISTPOS), and the list number (LISTNUM).
To specify the list entry associated with the list cursor for a certain list, code the LOCBYCURSOR and LISTNUM parameters.
See Understanding the List Cursor for information about using the list cursor with a WRITE request.

If you omit the LISTPOS parameter, the default value, is HEAD. So in effect, there is always a value for LISTPOS if one is needed.