To temporarily deny access to the database for a particular user account, you can lock the user account. If the user then attempts to connect, then the database displays an error message and does not allow the connection. You can unlock the user account when you want to permit database access again for that user. You can use Oracle Enterprise Manager Database Express (EM Express) to lock and unlock user accounts.
To lock or unlock a user account:
In EM Express, go to the Users page, as described in the “Viewing User Accounts" topic.
Click the desired user account.
From the Actions menu, select Alter Account.
The Alter Account page appears.
Do one of the following:
To lock the account, enable the Account Locked option, and then click OK.
To unlock the account, disable the Account Locked option, and then click OK.