The supplied ACF2 code for DSN3@ATH and DSN3@SGN will use xref(sgp) records
to define secondary authids.
If you issue the following commands, you might be able to identify what looks like ACF2
logonids that will be associated with secondry authids.
The key of the record will be the "secondary authid"
The data will be all the logonids that would be able to access the "secondary authid".
The ACF2/DB2 rules should be reviewed to see if the authids are referenced and being given access.
This should provide confirmation that the site is setup for and using secondary authids.