DB2 FOR LUW / DB2FORLUW / 970 - DB2

The DB2 Design Advisor (db2advis) may recommend a base table or 
MQT (BT) with a generated column whose expression is exactly 
identical to one of the BT's columns. 
 
This can occur if the following conditions are satisfied: 
- MDC recommendations are requested, i.e., the db2advis -m 
command line parameter's value contains C, e.g., -m C 
- The BT column data-type is either of CHAR, VARCHAR, GRAPHIC or 
VARGRAPHIC 
- The BT column statistics imply the column can benefit from 
being created as a dimension of an MDC table, i.e., column 
storage as an MDC dimension does not exceed maximum allowable 
inflation for a BT as an MDC table 
 
The following is an example recommendation that exhibits this 
issue: 
... 
-- LIST OF MODIFIED CREATE-TABLE STATEMENTS WITH RECOMMENDED 
PARTITIONING KEYS AND TABLESPACES AND/OR RECOMMENDED 
MULTI-DIMENSIONAL CLUSTERINGS 
-- =========================== 
-- table["TPCD    "."ORDERS"], Added table size     ....MB 
-- CREATE TABLE "TPCD    "."ORDERS" ( "O_ORDERKEY" INTEGER NOT 
NULL , 
--      "O_CUSTKEY" INTEGER NOT NULL , 
--      "O_ORDERSTATUS" VARCHAR(100) NOT NULL , 
--      "O_TOTALPRICE" DOUBLE NOT NULL , 
--      "O_ORDERDATE" DATE NOT NULL , 
--      "O_ORDERPRIORITY" CHAR(15) NOT NULL , 
--      "O_CLERK" CHAR(15) NOT NULL , 
--      "O_SHIPPRIORITY" INTEGER NOT NULL , 
--      "O_COMMENT" VARCHAR(79) NOT NULL , 
--   MDC............... VARCHAR(100) GENERATED ALWAYS AS ( 
(O_ORDERSTATUS) ) ) 
--     IN "TPCD_MDC" 
-- ORGANIZE BY ( 
--     MDC............... ) 
-- ; 
-- COMMIT WORK ; 
...

DB2 DESIGN ADVISOR MAY ERRONEOUSLY RECOMMEND A GENERATED COLUMN 
IDENTICAL TO A BASE COLUMN DURING MDC RECOMMENDATIONS.

Manually alter the recommended table DDL by removing the 
generated column definition and changing the name of the column 
in the ORGANIZE BY clause. 
For the above example recommendation, the DDL should be altered 
as follows: 
CREATE TABLE "TPCD    "."ORDERS" ( "O_ORDERKEY" INTEGER NOT NULL 
, 
     "O_CUSTKEY" INTEGER NOT NULL , 
     "O_ORDERSTATUS" VARCHAR(100) NOT NULL , 
     "O_TOTALPRICE" DOUBLE NOT NULL , 
     "O_ORDERDATE" DATE NOT NULL , 
     "O_ORDERPRIORITY" CHAR(15) NOT NULL , 
     "O_CLERK" CHAR(15) NOT NULL , 
     "O_SHIPPRIORITY" INTEGER NOT NULL , 
     "O_COMMENT" VARCHAR(79) NOT NULL  ) 
    IN "TPCD_MDC" 
ORGANIZE BY ( 
    O_ORDERSTATUS ) 
;

DB2 Version 9.7 Fix Pack 1 for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 2 for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 3 for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 3a for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 4 for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 5 for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 6 for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 7 for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 9a for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 8 for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 9 for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 10 for Linux, UNIX, and Windows
 

First fixed in DB2 UDB Version 9.7, FixPak 1

Manually alter the recommended table DDL by removing the 
 
generated column definition and changing the name of the column 
in the ORGANIZE BY clause. 
For the above example recommendation, the DDL should be altered 
as follows: 
CREATE TABLE "TPCD    "."ORDERS" ( "O_ORDERKEY" INTEGER NOT NULL 
, 
     "O_CUSTKEY" INTEGER NOT NULL , 
     "O_ORDERSTATUS" VARCHAR(100) NOT NULL , 
     "O_TOTALPRICE" DOUBLE NOT NULL , 
     "O_ORDERDATE" DATE NOT NULL , 
     "O_ORDERPRIORITY" CHAR(15) NOT NULL , 
     "O_CLERK" CHAR(15) NOT NULL , 
     "O_SHIPPRIORITY" INTEGER NOT NULL , 
     "O_COMMENT" VARCHAR(79) NOT NULL  ) 
    IN "TPCD_MDC" 
ORGANIZE BY ( 
    O_ORDERSTATUS ) 
;

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

20.08.2009
28.12.2009
28.12.2009

9.7.