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Status Delivered
Created by Guest
Created on Mar 11, 2024

CDC zOS Support Index with Identity Columns

Last week, during our testing of table replication with identity columns, it was discovered that CDC on zOS was unable to utilize primary indexes containing identity columns for replication. Since many tables utilize the identity column as the primary index key, this issue prevents CDC from replicating these tables.   IBM ssupport uggested changing the identity column to a regular column.  While this approach may work for some tables, it won't work for other tables that requies identity column be present for record creation.   
The proposed idea is to ignore the index with identity column and treat it as a regular index.  This will make this index as a 'qualifed' index for replication.  Similar behaviour is observed on CDC Db2 LUW.   

Needed By Month
  • Admin
    Davendra Paltoo
    Apr 30, 2024

    IBM Update

    PTF UI96691 for APAR PH60838 that addresses CDC-I-637 : CDC zOS Support Index with Identity Columns has been shipped.This PTF may still need 1 or 2 days to be visible/available for customers to download.

    Documentation in the knowledge center will also be updated. In the meantime, here is a brief description of this enhancement:

    1) A new parameter ALLOWGENERATEDKEY is introduced to control whether generated keys are allowed in replication index, the value can be YES or NO. NO is the default value, with this setting, CDC does not allow generated keys in replication index, as what CDC behaves without this feature. When ALLOWGENERATEDKEY is setting to YES, CDC allows GENERATED BY DEFAULT columns in replication index, but still does not allow GENERATED ALWAYS columns.
    The ALLOWGENERATEDKEY should be configured in CHCDBMXX member dataset.

    2) Unique index with GENERATED BY DEFAULT columns has the lowest rating, so when there are several qualifying indexes available for target table, by default, the one with GENERATED BY DEFAULT columns would not be chosen as replication index, but customer can choose it via MC Column Mappings -> Key Columns.. ->Specify Key -> Use an Index.
    If unique index with GENERATED BY DEFAULT columns is the only qualifying index, then CDC has no choice but to use it as replication index, in such situation, create table mapping will trigger warning message CHC1516W(Pop up in MC as well as issuing in CDC z/OS SPOOLed output), start refresh/mirror will trigger warning message CHC1519W, refresh/mirror can continue. Of course, those are only happening when ALLOWGENERATEDKEY=YES.

  • Guest
    Mar 26, 2024

    I am providing more information about the test case.  

    1) DDL on DB2 LUW

    Here is the DDL for creating table on Db2 LUW.

        "COL1" SMALLINT, 
        "COL2" INTEGER, 
        "COL3" DECIMAL(10 , 2), 
        "COL4" CHAR(10 OCTETS), 
        "COL5" VARCHAR(50 OCTETS), 
        "COL6" DATE, 
        "COL7" TIME, 
        "COL8" TIMESTAMP

    2) DDL on Db2 zOS

    CREATE TABLE DBATST0.TPAS_FIS_TO_TRP2                               
             (ID INTEGER                                                     
                                                             NOT NULL        
       GENERATED BY DEFAULT AS IDENTITY ( START WITH 1                       
             , INCREMENT BY 1                                                
             , MINVALUE 1                                                    
             , MAXVALUE 2147483647                                           
             , CACHE 20                                                      
             , NOCYCLE                                                       
             , NOORDER )                                                     
             ,COL1 SMALLINT                                                  
       WITH DEFAULT NULL                                                     
             ,COL2 INTEGER                                                   
       WITH DEFAULT NULL                                                     
             ,COL3 DECIMAL(10, 2)                                            
       WITH DEFAULT NULL                                                     
             ,COL4 CHARACTER(10) FOR SBCS DATA                               
       WITH DEFAULT NULL                                                     
             ,COL5 VARCHAR(50) FOR SBCS DATA                                 
       WITH DEFAULT NULL                                                     
             ,COL6 DATE                                                      
       WITH DEFAULT NULL                                                     
             ,COL7 TIME                                                      
       WITH DEFAULT NULL                                                     
             ,COL8 TIMESTAMP (6) WITHOUT TIME ZONE                           
       WITH DEFAULT NULL                                                     
             ,CONSTRAINT I37TST21 PRIMARY KEY                                
             IN PAS0037D.S37TST02                                            
        APPEND NO                                                            
        NOT VOLATILE CARDINALITY                                             
        DATA CAPTURE CHANGES                                                 
        AUDIT NONE                                                           
        CCSID EBCDIC;       


           ON DBATST0.TPAS_FIS_TO_TRP2     
          (ID ASC                          
           INCLUDE NULL KEYS               
           NOT CLUSTER                     
           DEFINE YES                      
           COMPRESS NO                     
           BUFFERPOOL BP0                  
           CLOSE YES                       
           DEFER NO                        
           COPY NO                         
           USING STOGROUP SYSDEFLT         
               PRIQTY -1                   
               SECQTY -1                   
               ERASE NO                    
           FREEPAGE 0                      
           PCTFREE 10                      
           GBPCACHE CHANGED                
           PIECESIZE 4194304K;          

    3) Error message received during mapping.

    ERROR : 

    CHC1508W: The selected table has no qualifying index. The table can be used for refresh, but a qualifying index must be created before it can be used for mirroring.  A qualifying index is a unique index with no nullable and no GENERATED ALWAYS columns.