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CDC Configuration using LT Replication server – 2

In blog post CDC Configuration using LT Replication server – 1 we have covered what is Data inconsistency and why it happens and what are tools provided by SAP to fix inconsistencies.

In this blog post we will deep dive into how to configure CDC using LT replication server and how to fix inconsistencies.

By exploring below steps we will achieve how CDC is configured.

  1. Pre requisites for CDC

  2. Configuration of CDC

  3. Run comparison and interpreting results

  4. Fixing inconsistencies discovered by CDC

 

1.Pre-requisites for CDC

Following are the technical prerequisites which must be fulfilled before using the SAP Solution Manager for Cross Database Comparison:

  1. Correct versions of the software components
  2. Activation of needed services
  3. Authorization for users
  4. Connections to the data source system

1. Correct versions of the software components

To setup CDC, it is highly recommended to have the latest ST-PI and ST-A/PI addons installed on the managed ABAP systems.

Further information on latest release will be available here and also refer to SAP Note 521820.

Based on the version implement relevant notes related to the software version you are in. Further details can be found in this WIKI

2. Activation of needed services

Activate below services from SICF

  • WDA_DSWP_CDC_MAINis mandatory for the main application
  • WD_DSWP_CDC_ACFif you want to compare XML files from your local PC
  • WDA_DSWP_CDC_GENERATIONif you want to use mass generation of comparisons
  • WDA_DSWP_CDC_GENER_INSTif you want to use mass generation of comparisons
  • WDA_DSWP_CDC_GROUP_Mif you want to use comparison groups

3. Authorization for users

Following different types of authorizations and template roles which can be used to create required roles and run CDC comparison in solution manager:

  • Development: The object modeler role SAP_CDC_OBJECT_MODELER can create/change/delete comparison objects to perform the modelling and generation but is not allowed to create a comparison instance of it.
  • Administration: The instance creator role SAP_CDC_INSTANCE_CREATOR can display and use comparison object to create/change/delete comparison instances but cannot change the comparison object model.
  • Scheduling: The instance executer role SAP_CDC_INSTANCE_EXECUTER can execute and reorganize the comparison run but can neither output the result nor change the comparison objects and instances.
  • Result Analysis: The instance analyzer role SAP_CDC_INSTANCE_ANALYSER can output the result (business data), but cannot execute the run himself, nor change the comparison object and instances.

CDC authorization objects on Managed System:

Create a role using template role SAP_CDC_DATA_READER and assign below authorization objects based on requirement:

S_DEVELOP, S_RFCACL, S_RFC

For comparison with HANA DB a DBCON connection should be maintained in DBACOCKPIT. On the remote database, the DB login user needs to have read-only access in the application schema for all tables used in the CDC data model.

4. Connections to the data source system

Once we have latest version and required users created, next step is to create connections to Managed system from Solution Manager system.

In current scenario we are using Source 1 which is S4HANA ABAP and Source 2 is HANA DB using LT Replication server.

For this scenario we need to have below connections:

  1. RFC Type 3 connection from Solution Manager to S4HANA system
  2. DBCO connection in Solution Manager with Source 2 details
  3. RFC Type 3 connection form LT replication server to SolMan and from SolMan to LT server

2. Configuration

Once these pre-requisites are in place we will now work on configuring CDC. Below are the steps for the same.

Below are the steps to configure CDC using LT Replication server option for Mass activities

 

Access CDC from SM_WORKCENTER–>Data–>CDC

SM_WORKCENTER

Click on CDC. From below screen click on Mass Processing which uses SLT replication server for comparison.

In next step select Create Comparison Using Data from LT Replication Server option

In the next screen there are few inputs we need to select for comparison.

  1. Select Generate only for Source Type with Automatic Generation from drop down
  2. Enter table name in Prefix tab
  3. Enter Max No. Differences – further details provided in Appendix
  4. Enter Block Size – further details provided in Appendix
  5. Enter the ABAP source system RFC
  6. Enter the ADBC connection of Target system
  7. Enter the RFC to SLT system
  8. Enter the MT ID of SLT

Enter above details and click on Next.

Here Select the table which is required for comparison and click Next

In next screen we will see Comparison details and the Data Model which is auto populated

Validate the Data Model and make necessary changes and click Next

In this scenario we are not selecting any Comparison Group data.

Select NO_GROUP and click Next

In next screen review all the parameters provided till now and click Submit

Once parameters are reviewed click on Back to Cross-Database Comparison

3. Run comparison and interpreting results

Now you can see the table which we have created. Next step will be start comparison.

Select the table and click on Start

There are few options which we can select here, as this is first run we are selecting Create Job and Start Immediately

Job status can be viewed by clicking on Instance run.

We can see the progress of the comparison.

Once comparison is completed, results can be interpreted form below screen.

Inconsistency Identified Action Taken by SAP LT Replication Server
Objects exist in the source system, but not in the target system. SAP LT Replication Server inserts the missing rows in the target system
Objects exist in the target system but not in the source system SAP LT Replication Server removes the rows from the target system.
Objects exist in both systems, but there are differences regarding data SAP LT Replication Server adjusts the values in the target system so that they are consistent with the values in the sender system

4. Fixing inconsistencies discovered by CDC

These inconsistencies between two tables can be fixed using SLT server.

Next step is to login to SLT system–>Select MT ID–>Expert Functions–> Resolve Inconsistencies Identified by CDC Application

You must specify an RFC connection from the LTR system to the CDC system. The system uses this RFC connection to identify the relevant mass transfer IDs, tables, CDC instances, and CDC runs.

Note: You can only resolve inconsistencies for tables that have the status In Replication and only one table inconsistency can be fixed once.

Appendix

Further information related to CDC:

CDC Wiki

Useful SAP Notes:

2081759 – Monitoring of SLT systems in Solution Manager using the System Monitoring application

2761769 – What to check if the inconsistency between source table and target table is found. – SAP Landscape Transformation replication server

2602264 – Is there a way to check source and target consistency? – SLT

Regards

Phani.

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