Central resource registration selection function (function code X'05')

The central resource registration selection function is invoked at a network node before it sends a central resource registration request to a CDS. When VTAM® passes the CDS list to the exit, the first entry in the list identifies the CDS with the least weighted path. The remainder of the list continues in least weighted order for all other known CDSs in the network. The exit can approve the list as received or reorder the list. VTAM sends all central resource registration requests to the first CDS returned in the list and any other CDS entries returned are not used. VTAM continues to use this CDS for registration requests until a topology change occurs in the network involving one or more CDSs. When a change occurs and more than one CDS exists in the network, the exit is reinvoked to select the CDS to use.

The following conditions in the returned CDS list are not valid and result in VTAM issuing a FFST™ probe, deactivating the function, and continuing with the original list.

No entries are returned in the list.
Entries are added that are not in the original list.
Duplicate entries are found in the list.
Entries are found that contain corrupted data.

No search-related information is passed to the exit for central resource registration selection.

The user-written exit returns to VTAM with a return code:

Register 15:

Return code

X'00' (0): The CDS list has been modified.
X'04' (4): The CDS list has not been modified.

An unexpected return code is treated as return code X'04', but message IST1183I is issued to record the unexpected return code.