Making the previous Performance Document non-editable

Content

Hello Oracle Community,

Desired result: I would like to make the previous performance document period non-editable by the users. 

Actions that I made: 
Under the 'Manage Performance Templates' >> Documents Period >> uncheck the 'Available to Use' box. After that I was expecting that the related performance documents become non-editable for the users. However, it seems like nothing is changing with this step. 

Question: do you know what this check box is used for and how can I make the previous review documents non-editable without creating a new period?

Thank you,
Dóra