Thank you for your answer. In case I am afraid account does not exist, and samples were not installed :
what I do :
sql>connect sys as sysdba
sql> alter user HR identified by HR account unlock
ORA-01918 : user does not exist
I think Samples HR,... are not installed : script hr_main.sql is not present in directory ...\product\12.1.0\dbhome_1\demo\schema\human_resources.
If i' am wright, where can I load Samples to complet product before install ?