Hi
Had the same issue today and found the solution, so I'll post it:
Snapshots can be viewed by: "SELECT * FROM "SYS"."M_SNAPSHOTS".
"Be aware that this command fails if snapshots exist
(“general error: Shrink canceled, probably because of
snapshot pages”). In this case you can proceed
according to SAP Note 1999880 (“How can
RECLAIM DATAVOLUME be executed when system
replication is active?”)."