VTAM® constructs a dynamic adjacent SSCP table in the order in which the CDRM-CDRM sessions are established. Therefore, the search order for a resource might not be the same as that which can be achieved using a statically defined adjacent SSCP table. Extra session establishment time might be required if the SSCP list contains many entries or if it is arranged so that several SSCPs must be tried before the owning SSCP can be located. However, to control the order of search in this case, you can use the session management exit routine (adjacent SSCP selection function) in conjunction with a dynamic adjacent SSCP table.

In the session management exit routine, the adjacent SSCP selection function for LU-LU sessions allows you to modify the list of SSCPs in the search. You can shorten or reorder the list of SSCPs from which the next SSCP used in session setup is chosen during session request routing, or you can decide not to route at all.

The list that the session management exit routine receives as input is either an adjacent SSCP table or a list of adjacent SSCPs that is built during the previous LU-LU session setup for the same resource. If no adjacent SSCPs exist, this function is not invoked. If you do not provide this function in your session management exit routine, VTAM uses the adjacent SSCP table as it exists.

z/OS Communications Server: SNA Customization describes the adjacent SSCP selection function of the session management exit routine.