Wait state event codes and IDs are used to determine why VTAM® is in a wait state.
SSCP, PU services, LU services, and network operator services processes that are in wait states are represented by a waiting request element (WRE) queued off the LQAB of the subcomponent that controls the waiting process. The WRE for a process contains a 2-byte event code that identifies the event so you do not have to look at the event ID itself.
See z/OS Communications Server: SNA Diagnosis Vol 1, Techniques and Procedures for an overview of the wait procedure.