Is there a way to identify all SITuations that are coded with MISSING?

To accomplish this, you can create a MissingSits.sql file (with a SELECT statement as shown below:

SELECT SITNAME, PDT FROM 04SRV.TSITDESC WHERE PDT LIKE '*MISSING*';

Then run the SPUFIL (zOS) kdstsns (Windows) or a ./kdstsns (AIX) command against it:

Use the following modify commands if HUB is on zOS:
/F <tems_starttaskname>,CTDS START SPUFIL FileNameYouCreated
/F <tems_startetaskname>,FLUSH

For Windows, use the kdstsns MissingSits.sql *hub > diagnode.lst,
= or = just type kdstsns to be prompted.

For UNIX, then similarly, but issue ./kdstsns