What is the effect of specifying the “ENABLE PLUGGABLE DATABASE” clause in a “CREATE DATABASE”
statement?
A.
It will create a multitenant container database (CDB) with only the root opened.
B.
It will create a CDB with root opened and seed read only.
C.
It will create a CDB with root and seed opened and one PDB mounted.
D.
It will create a CDB that must be plugged into an existing CDB.
E.
It will create a CDB with root opened and seed mounted.
Explanation:
* The CREATE DATABASE … ENABLE PLUGGABLE DATABASE SQL statement creates a new CDB. If you
do not specify the ENABLE PLUGGABLE DATABASE clause, then the newly created database is a non-CDB
and can never contain PDBs.
Along with the root (CDB$ROOT), Oracle Database automatically creates a seed PDB (PDB$SEED). The
following graphic shows a newly created CDB:
* Creating a PDB
Rather than constructing the data dictionary tables that define an empty PDB from scratch, and then populating
its Obj$ and Dependency$ tables, the empty PDB is created when the CDB is created. (Here, we use empty to
mean containing no customer-created artifacts.) It is referred to as the seed PDB and has the name
PDB$Seed. Every CDB non-negotiably contains a seed PDB; it is non-negotiably always open in read-only
mode. This has no conceptual significance; rather, it is just an optimization device. The create PDB operation is
implemented as a special case of the clone PDB operation.
