Trying to understand acfs snapshot management

Hi,

I need help understanding how ACFs manages disk space for deleted snapshots.

I have an environment with over 30 PDBs, most of which currently only contain the structure, no data. Below is a list of them.

SQL> select p1.con_id, p1.name ,p1.OPEN_MODE ,(p1.total_size/1048576/1024) size_gb ,p1.guid from v$pdbs p1;

CON_ID|NAME |OPEN_MODE | SIZE_GB|GUID
------|-------------------------|----------|---------|---------------------------------
2|PDB$SEED |READ ONLY | 1.38|304E30745055B1DEE0639403F50AC8D0
3|PDB_TEMPLATE |READ ONLY | 5.38|305317DBDD0320CEE0639403F50A5A91
5|PDB_DMV_N2_MASTER |READ WRITE| 5.38|3EEC64A75DB42DACE0639403F50AA7E7