对于12.1版本数据库而言
37.2.1 Decide How to Configure the CDB --搜索文档 Prepare to create the CDB by research and careful planning. Table 37-1 lists some recommended actions and considerations that apply to CDBs. For more information about many of the actions in Table 37-1, see Table 2-1. Table 37-1 Planning for a CDB Action Considerations for a CDB Additional Information Plan the tables and indexes for the pluggable databases (PDBs) and estimate the amount of space they will require. In a CDB, most user data is in the PDBs. The root contains no user data or minimal user data. Plan for the PDBs that will be part of the CDB. The disk storage space requirement
for a CDB is the space required for the Oracle Database installation plus the sum of the space requirements for all of the PDBs that will be part of the CDB.
A CDB can contain up to 253 PDBs, including the seed.最大253（且包含种子pdb）
对于12.2版本数据库而言
37.2.1 Decide How to Configure the CDB
Prepare to create the CDB by research and careful planning.
Table 37-1 lists some recommended actions and considerations that apply to CDBs. For more information about many of the actions in Table 37-1, see Table 2-1.
Table 37-1 Planning for a CDB
In a CDB, most user data is in the PDBs. The root contains no user data or minimal user data. Plan for the PDBs that will be part of the CDB.
The disk storage space requirement for a CDB is the space required for the Oracle Database installation plus the sum of the space requirements
for all of the PDBs that will be part of the CDB. A CDB can contain up to 4,096 PDBs,
but you can limit the CDB to a smaller number of PDBs by setting the MAX_PDBS
initialization parameter.
You can also create application containers in a CDB. An application container is a collection of application PDBs
that store the data for one or more applications. In addition, application containers support user-created application
common objects that can be shared by the application PDBs in the application container.