ORA-02096: specified initialization parameter is not modifiable with this option

Since version 11g must use the DEFERRED clause. It means it takes effect in subsequent sessions.

You must exit from current session to get the new settings

SQL Profile

When you run SQL Tuning Advisor, sometimes you can see findings for SQL Profile:
1- SQL Profile Finding (see explain plans section below)
--------------------------------------------------------
  A potentially better execution plan was found for this statement.


  Recommendation (estimated benefit: 99.99%)
  ------------------------------------------
  - Consider accepting the recommended SQL profile.
    execute dbms_sqltune.accept_sql_profile(task_name => 'staName61543', task_owner => 'PWRLINE', replace => TRUE);

12c Query Against Dictionary Views slow

Doc ID 1292253.1

SQL> purge recyclebin; --if you have DBA access, purge dba_recyclebin;
SQL> EXEC DBMS_STATS.GATHER_TABLE_STATS(OWNNAME =>'SYS', TABNAME => '$KTFBUE',ESTIMATE_PERCENT=>100);
SQL> EXEC DBMS_STATS.GATHER_SCHEMA_STATS('SYS');
SQL> EXEC DBMS_STATS.GATHER_FIXED_OBJECTS_STATS(NO_INVALIDATE => FALSE);