Many situation client want to go for maintenance mode when do the major Production deployment or upgrade project deployment, Salesforce has “freeze” option on the user record level.
When you click “Freeze” button that user prevented to logging in to org. Actually Salesforce making “IsFrozen” checkbox field value to TRUE on the User object.
Note: Freeze not going to release user license to use in your organization.
You can use apex dataloader(version 29 or later) to freeze more than one user in your organization.