To be complete, the IPCS SUMMARY COMMAND dispatchablity information needs to go beyond TCBFLGS4 and also include WEB dispatchablity information plus more

From IPCS, the SUMMARY command is widely used to determine the state of a TCB in a given address space. That includes the TCBFLGS4 non-dispatiblity flags. For example, if a TCB was in an RB wait via the Wait service,  IPCS would state that 'Top RB is in a wait' for the user to know it is waiting. However, if the Top RB had used the Pause server to "wait" rather than the wait service, that would not be shown making the user think the task is dispatchable.  I've seen many knowledgeable people miss this important fact and thinking the task is dispatchable.

IPCS SUMMARY analysis of TCBs should use the non-dispatablity flags indicated in the WEB (work element block)'s WEBNDFLGS to determine the true dispatchable state of a TCBs These include non-dispatchablily Due to Paused Service, Suspended waiting for Local Lock, Due to Swap Out, etc. . In addition to the WEB's non-dispatchablity indications, there are time stamps related to the last dispatch time (WEB_TOD_LastTimeWuqAdded), when it was suspended for the local lock etc..
WEBs are the true control block represented dispatchablity. They were added many years ago but IPCS SUMMARY was never updated to include them. IPCS IEAVWEBI was added and it already provides much of this information. The problem is knowing about IEAVWEBI and tying it together with the SUMMARY output. Having summary display that key information would make everyone's life easier.  

IEAVWEBI service: 

PLEASE SPECIFY EITHER ''ALL'' OR ''WUQ'' OR ''TCB ASID(XXXX)'' OR ''SRB ASID(XXXX)'' OR
''ASID(XXXX):'' OR ''EXIT'' !
• !
• ALL - Displays high level statistics about WEBs within the system. !
• WUQ - Displays all WEBs known within the system that are on a WUQ. !
• TCB ASID(xxxx) - Displays TCB WEBs for that ASID using ASCBTAWQ. !
• SRB ASID(xxxx) - Displays SRB WEBs for that ASID using ASCBSAWQ. !
• ASID(xxxx) - Displays all WEBs for that ASID.