There are two traces available that will show the ALTID being switch to for USS paths:
The EN$TRAUI is the standard trace for the ALTID. It will show the swap differently for USS paths than standard files. If one sees the following entry in the trace it means the swap is being done for a USS path.
C1UIO000: FUNCT MAIN ENDEVOR ALTERNATE ID SWAP ON
The C1UIO000 is the key for noting the ALTID was swapped for a USS path – but the path name is not provided as part of the trace.
The EN$TRUSS trace also will show the ALTID being switch but also show the path name.
$USS C1UIO000 C1UIO000 SWAP TO ALTID
$USS C1UIO000 DIRLRUTN BPX1OPD opendir /00000000/00000000/00000000/ File ID(….
$USS C1UIO000 DIRLRUTN /CA31/u/users/endevor/P9999/stg1/base/
$USS C1UIO000 C1UIO000 SWAP BACK TO USERID
It is recommended to use both traces if having a problem or question on the ALTID and USS paths.
In neither trace will one be able to see the actual ID’s being swapped for USS paths.