How To Fix DMC_RT_MSG235 - Secondary index contains duplicate values

SAP Error Message - Details

• Message type: E = Error

• Message class: DMC_RT_MSG - DMC: Runtime Object Messages

• Message number: 235

• Message text: Secondary index contains duplicate values

What causes this issue?

The system cannot either insert a record or update a record in the
target system table, as this would violate a unique secondary index for
the table.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

System Response

The system stops the transfer of records to the target system.

How to fix this error?

By default, to improve performance, the system first reads the entries
from the logging tables in the order of the key fields of the source
table, then reads the entries in the order of the key field of the
logging table (field IUUC_SEQUENCE). This means that the order in which
changes occur in the source system is not considered, which could result
in a potential conflict for the secondary index in the target system. To
preserve the order of the changes in the source system, you can
configure SAP LT Replication Server such that the entries are only read
from the logging table in the order of field IUUC_SEQUENCE.
Two options are possible:
Remove the unique secondary index from the target table<(>,<)> or change
it to a non-unique secondary index. If necessary<(>,<)> reset the status
of the table in the central system. The central system will start
replicating data from the source system table to the target system table
again.
If you want to keep the unique secondary index in the target system<(>
,<)> set the field READ_SEQU_ORDER in table IUUC_PERF_OPTION to ?X? and
reload the table. The SAP LT Replication Server system will read the
entries from the logging table in the order of the key field of the
logging table (field IUUC_SEQUENCE), therefore preserving the order of
the changes in the source system. However, performance is not optimized.
Note that you cannot use the option <ZK>Use Key Fields to Calculate
Ranges</> in transaction LTRS.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message DMC_RT_MSG235 - Secondary index contains duplicate values ?

  The SAP error message DMC_RT_MSG235 indicates that there are duplicate values in a secondary index, which can lead to issues in data processing, especially in scenarios involving data migration or replication. This error typically arises in the context of SAP Data Migration Cockpit (DMC) or when working with data models that rely on unique constraints.
  Cause:
  The primary cause of this error is the presence of duplicate entries in the fields that are defined as part of the secondary index. This can happen due to:
  
  Data Quality Issues: The source data may contain duplicates that violate the uniqueness requirement of the secondary index.
  Incorrect Data Mapping: During data migration, if the mapping of fields is not done correctly, it can lead to duplicates being created.
  Concurrency Issues: If multiple processes are inserting or updating records simultaneously, it may lead to duplicates being created in the secondary index.
  
  Solution:
  To resolve the DMC_RT_MSG235 error, you can follow these steps:
  
  
  Identify Duplicates:
  
  Use SQL queries or data profiling tools to identify the duplicate records in the source data. You can group by the fields that are part of the secondary index and count occurrences to find duplicates.
  
  
  
  Clean Up Data:
  
  Once duplicates are identified, you need to decide how to handle them. Options include:
  
  Removing duplicates if they are not needed.
  Merging records if they contain complementary information.
  Updating records to ensure uniqueness.
  
  
  
  
  
  Review Data Mapping:
  
  Check the data mapping configuration in the migration or replication process to ensure that it is set up correctly and does not inadvertently create duplicates.
  
  
  
  Adjust Index Configuration:
  
  If the secondary index is not required for your use case, consider adjusting the index configuration to remove the uniqueness constraint, if appropriate.
  
  
  
  Test Migration:
  
  After cleaning the data and adjusting configurations, perform a test migration to ensure that the error does not occur again.
  
  
  
  Monitor for Concurrency Issues:
  
  If the issue is related to concurrent processes, consider implementing locking mechanisms or adjusting the process flow to prevent simultaneous updates that could lead to duplicates.
  
  
  
  Related Information:
  
  Data Migration Cockpit (DMC): A tool used for data migration in SAP systems, which provides functionalities for data mapping, validation, and execution.
  Secondary Indexes: These are used in databases to improve the performance of queries. They can enforce uniqueness on certain fields, which is crucial for maintaining data integrity.
  Data Quality Management: Implementing data quality checks and validation rules can help prevent issues related to duplicates in the future.
  
  By following these steps, you should be able to resolve the DMC_RT_MSG235 error and ensure that your data migration or replication processes run smoothly.