Tuesday, September 30, 2014

12c PDBs and SPFILE

In 12c multi-tenant database, the spfile is for CDB only. A newly created PDB will inherit the initialization values from the container database if they are created from the pdb$seed ( default empty PDB). 
 There are about 184 parameters that can be modified at the PDB level and are stored in the sys table of the PDB. If you altered the parameter in a PDB  and then plugged in to a different Container database, these modified parameters go with the PDB.

The v$system_parameter shows the different configured parameters of all plugged in database. To see all non default parameters, you can run the following query.
select  name,value, con_id from v$system_parameter where con_id!=0;

One interesting fact is, once a parameter has been set, later even if you reset the value equal to container default, the PDB will still maintain the parameter values.