Rule Definition
CHAR should be used for storing fix length character strings. String values will be space padded before stored on disk. If this type is used to store variable length strings, it will waste a lot of disk space. So, Oracle suggests to use VARCHAR2 / NVARCHAR2 instead of CHAR / NCHAR while declaring datatype. Also VARCHAR is going to be replaced by VARCHAR2 in future so Oracle recommends to replace VARCHAR by VARCHAR2.

Remediation
Change CHAR columns / variables / parameters to VARCHAR2. Change VARCHAR columns / variables / parameters to VARCHAR2. Change NCHAR columns / variables / parameters to NVARCHAR2.

Violation Code Sample

Use Case 1 :
CREATE TABLE leaders
(
 lead_name  varchar2(12) null,
 lead_id    char(6) not null,
 lead_add   varchar2(40) null
)
/

Use Case 2 :
CREATE PROCEDURE remove_leaders (par_lead_name NCHAR(10)) AS
BEGIN
  DELETE FROM leaders
  WHERE leaders.lead_name = par_lead_name;
END;
/

Fixed Code Sample

Use Case 1 :
CREATE TABLE leaders
(
 lead_name  varchar2(12) null,
 lead_id    varchar2(6)  not null,
 lead_add   varchar2(40) null
)
/

Use Case 2 :
CREATE PROCEDURE remove_leaders (par_lead_name NVARCHAR2(10)) AS
BEGIN
  DELETE FROM leaders
  WHERE leaders.lead_name = par_lead_name;
END;
/