Oracle label security
The federated server supports Oracle Label Security, which you can use to secure data and ensure that only users with the appropriate authority can see it.
Administrators can use Oracle Label Security to apply security policies to each row in a table. The security policies determine a user's level of access to the data, based on the authorities that are granted to the user ID or session ID. When you create a nickname on an Oracle data source object, the federated server automatically detects whether the data source uses Oracle Label Security. If Oracle Label Security is being used, the nickname is not cached.
You can use the ALTER NICKNAME statement to allow or disallow caching. For example, if you created a nickname on a data source object with Oracle Label Security before federated support for this feature was available, you can alter the nickname to disallow caching. If you created a nickname on a data source object with Oracle Label Security and Oracle Label Security is removed, you can alter the nickname to allow caching.
A database administrator can choose to hide a label to prevent some users from knowing that a particular row exists. In this case, the column is hidden in the table. Nicknames with hidden label columns are not cached.