Uses the DBMS_REDACT package.
The following procedures can be used …

• ADD_POLICY
• ALTER_POLICY
• DISABLE_POLICY
• DROP_POLICY
• ENABLE_POLICY

The following Function Types are available …

• DBMS_REDACT.NONE
• DBMS_REDACT.FULL
• DBMS_REDACT.PARTIAL (Number, Character, Date)
• DBMS_REDACT.RANDOM

The below examples fully redacts all details in the card_no column.

BEGIN
  DBMS_REDACT.add_policy(
    object_schema => 'c##ian',
    object_name   => 'payment_details',
    column_name   => 'card_no',
    policy_name   => 'redact_card_info',
    function_type => DBMS_REDACT.full,
    expression    => '1=1'
  );
END;

There is a EXEMPT REDACTION POLICY privilege.
CTAS commands against a redacted table will fail.
Redaction does not apply to the WHERE clause.

Oracle Base Article