Which of the following ALTER SYSTEM statements can be run from within a pluggable database (PDB)?

In a multitenant environment, ALTER SYSTEM statements that affect instance-wide, shared resources (like the SGA or redo log files) must be executed from the root container. However, statements that affect only a specific Pluggable Database (PDB) can be run from within that PDB. ALTER SYSTEM CHECKPOINT when run from a PDB defaults to a local checkpoint for that PDB only. Similarly, ALTER SYSTEM ENABLE/DISABLE RESTRICTED SESSION when run from a PDB puts only that specific PDB into restricted mode, not the entire instance.

B. FLUSH BUFFERCACHE affects the entire System Global Area (SGA), which is shared by all PDBs, and thus must be run from the root container.
C. SWITCH LOGFILE affects the instance-wide redo log files, which are a shared resource for the entire CDB, and must be run from the root.

1. Oracle Database 23ai, SQL Language Reference, "ALTER SYSTEM". The documentation includes a section "Usage in a Multitenant Environment" which specifies which clauses are permissible within a PDB.

2. Oracle Database 23ai, Multitenant Administrator's Guide, Chapter 3, "Administering a CDB", Section "Executing ALTER SYSTEM Statements in a CDB". This section explicitly lists which ALTER SYSTEM clauses are allowed or disallowed in a PDB. It confirms that CHECKPOINT (as a local checkpoint) and ENABLE/DISABLE RESTRICTED SESSION are allowed.