Changing Instance Parameter in Pluggable Database

As we know in Multi-tenant architecture we have only one instance at container level hence we have only one spfile for Container Database.

So value we set in parameters are associated in CDB$ROOT so applied to cdb root and serve as default parameters for all other containers;

Although we can set some pdb specific value for PDBs where ispdb_modifiable is true.

Let us understand by example.

Check some parameters from v$parameter view where ispdb_modifiable=’TRUE’

SQL> select name,value,ispdb_modifiable from v$parameter where ispdb_modifiable='TRUE';

NAME                 VALUE                ISPDB_MODIFIABLE
-------------------- -------------------- --------------------
sessions             472                  TRUE
timed_statistics     TRUE                 TRUE

Let us change sessions parameters to a different value in pdb then cdb.

I have changed sessions value to 300 in pdb2.

SQL>  alter session set container=pdb2;

Session altered.

SQL> alter system set sessions=300;

System altered.

I have changed sessions value to 200 in pdb1;

From cdb root, we can check pdb specific values in pdb_spfile$ view.

SQL> select pdb_uid,name,value$,db_uniq_name from pdb_spfile$ where name='sessions'
  2  ;

   PDB_UID NAME                 VALUE$               DB_UNIQ_NAME
---------- -------------------- -------------------- --------------------
1351741780 sessions             200                  db121
1899104254 sessions             300                  db121

We can see pdb specific values here.

Stay tuned for More articles on Oracle Multitenant

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