List parameters in a container database

To see the list of parameters in a container database, use can use the following query.

select name,value,display_value, default_value,isdefault,
    case 
     when issys_modifiable = 'FALSE'     then  'Change must go to spfile. Restart of cdb required'
     when issys_modifiable = 'IMMEDIATE' then  'Current sessions will pick up new value.'
     when issys_modifiable = 'DEFERRED'   then 'Future sessions will pick up the new value'
     else issys_modifiable
    end "issys_modifiable",
     case 
     when ispdb_modifiable = 'TRUE' then 'Parameter can be set in PDB'
     when ispdb_modifiable = 'FALSE' then 'Parameter cannot be set in PDB'
    end "ispdb_modifiable" 
    from v$system_parameter; 

Example output shows that the parameters can be set at different levels in your multitenant database structure

NAME	VALUE	DISPLAY_VALUE	DEFAULT_VALUE	ISDEFAULT	issys_modifiable	ispdb_modifiable
sga_max_size	8287944704	7904M	0	TRUE	Change must go to spfile. Restart of cdb required	Parameter cannot be set in PDB
shared_pool_size	671088640	640M	134217728	FALSE	Current sessions will pick up new value.	Parameter can be set in PDB
sga_target	8287944704	7904M	0	FALSE	Current sessions will pick up new value.	Parameter can be set in PDB
sort_area_size	65536	65536	65536	TRUE	Future sessions will pick up the new value	Parameter can be set in PDB

* Some parameters may only be written to the spfile and the CDB instance must be restarted.
* Other parameters may be set in the CDB and will be picked up in the individual PDBs, either affecting current sessions or future sessions only
* Some parameters may be set in each PDB, regardless of the CDB parameter value for the same parameter is set to


"Listing the Modifiable Initialization Parameters in PDBs Oracle 19c" is documented here

The v$system_parameter view in Oracle 19c is documented here