You are connected to a multitenant container database (CDB) with DBA privileges. The STATISTICS_LEVEL parameter is PDB_MODIFIABLE. You issue: SQL> ALTER SYSTEM SET STATISTICS_LEVEL=ALL SCOPE=BOTH…

Open PDBs that have not set their own PDB-level override for STATISTICS_LEVEL inherit the CDB root value, so they are updated to ALL immediately when the CDB root setting changes.

The SCOPE=BOTH clause includes SCOPE=MEMORY, which causes the parameter to take effect immediately in the running CDB root instance.

The persistent component of SCOPE=BOTH stores the new value so that any PDB currently closed will receive STATISTICS_LEVEL=ALL when it is subsequently opened.

Not all PDBs can be updated immediately because closed PDBs have no active memory to modify; they only inherit the new setting at open time, so an immediate effect across all PDBs regardless of state is not possible.

For PDB_MODIFIABLE parameters set from the CDB root, the persistent value is stored in the root container's parameter store and propagated to PDBs at open time rather than being written as a conventional SPFILE entry that applies globally to all containers.