alter system pdb scope and persistent

[oracle@stormking cdb12102 pdbcreate]$ sqlplus /nolog

SQL*Plus: Release 12.1.0.2.0 Production on Sun Apr 12 15:48:12 2015

Copyright (c) 1982, 2014, Oracle.  All rights reserved.

SQL> conn bf/bf@//stormking:1521/pdbg as sysdba
Connected.
SQL> show parameter optimizer_capture_sql_plan_baselines

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
optimizer_capture_sql_plan_baselines boolean     FALSE
SQL> alter system set optimizer_capture_sql_plan_baselines = true;

System altered.

SQL> shutdown immediate
Pluggable Database closed.
SQL> startup
Pluggable Database opened.

The change is persistent across pdb close/open:

SQL> show parameter optimizer_capture_sql_plan_baselines

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
optimizer_capture_sql_plan_baselines boolean     TRUE

The change is limited to pdb scope:
SQL> conn / as sysdba
Connected.
SQL> show parameter optimizer_capture_sql_plan_baselines

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
optimizer_capture_sql_plan_baselines boolean     FALSE