Rule Definition
A clustered index defines the order in which data is physically stored in a table. Table data can be sorted in only way, therefore, there can be only one clustered index per table. Always define a clustering index. Otherwise, DB2 will consider the first index that is created on the table as the implicit clustering index. In SQL Server the primary key constraint automatically creates a clustered index on that particular column(s).

Remediation
Consider adding a clustered index.

Violation Code Sample

CREATE TABLE DSN8A10.EMP
      (EMPNO     CHAR(6)                          NOT NULL,
       FIRSTNME  VARCHAR(12)                      NOT NULL,
       MIDINIT   CHAR(1)                          NOT NULL,
       LASTNAME  VARCHAR(15)                      NOT NULL,
       WORKDEPT  CHAR(3)                                  ,
       PHONENO   CHAR(4)         CONSTRAINT NUMBER CHECK
                 (PHONENO >= '0000' AND
                  PHONENO <= '9999')                      ,
       HIREDATE  DATE                                     ,
       JOB       CHAR(8)                                  ,
       EDLEVEL   SMALLINT                                 ,
       SEX       CHAR(1)                                  ,
       BIRTHDATE DATE                                     ,
       SALARY    DECIMAL(9,2)                             ,
       BONUS     DECIMAL(9,2)                             ,
       COMM      DECIMAL(9,2)                             ,
       PRIMARY KEY (EMPNO)                                ,
       FOREIGN KEY RED (WORKDEPT) REFERENCES DSN8A10.DEPT
                 ON DELETE SET NULL                       )
  EDITPROC  DSN8EAE1
  IN DSN8D10A.DSN8S10E
  CCSID EBCDIC;

Fixed Code Sample

CREATE INDEX DEPT_IX
  ON EMP
    (DEPTNO ASC)
     CLUSTER;

https://www.ibm.com/support/knowledgecenter/SSEPEK_10.0.0/intro/src/tpc/db2z_clusteringindexes.html https://docs.microsoft.com/en-us/sql/relational-databases/indexes/clustered-and-nonclustered-indexes-described?view=sql-server-ver15 http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.infocenter.dc32300.1570/html/sqlug/X50317.htm