You can save the state of PDBs in 12.1.0.2. When you start the container, Oracle will place each PDB in its saved state whether it was open or closed at shutdown:
https://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:9531671900346425939 You should only use the trigger trick in 12.1.0.1.