A list entry can be located by its assigned entry identifier (ENTRYID). Prior to OS/390® Release 9, the system assigned an ENTRYID when the list entry was created and assured that the ENTRYID was unique among the list entries previously and currently allocated in the list structure.

With OS/390 Release 9 and higher, an allocation attribute can specify whether the list structure is to be allocated with system-assigned ENTRYIDs or user-assigned ENTRYIDs. The IXLCONN ENTRYIDTYPE=USER parameter indicates that the user will assign the ENTRYID for each list entry created, and will assure that the ENTRYID is unique among the list entries currently allocated in the list structure. Unlike a system-assigned ENTRYID, which is never reused and is unique for the life of the structure, a user-assigned ENTRYID can be reused over time provided it is unique while assigned to a list entry.

To use user-assigned ENTRYIDs, the list structure must be allocated in a coupling facility of CFLEVEL=8 or higher or the connect request will be rejected. An IXLCONN request to connect to an allocated structure also will be rejected if the ENTRYIDTYPE attribute does not match the attribute currently in effect for the structure. Similarly, an IXLCONN REBUILD request will be rejected if the connector's requested ENTRYIDTYPE attribute does not match the attribute in effect for the original structure.

The type of list entry identifier is consistent for the entire list structure. Either all list entries are referenced by system-assigned ENTRYIDs or all list entries are referenced by user-assigned ENTRYIDs.