RDS  IBM Db2 LUW

Potential performance impact when converting  standby to Multi-AZ

Your DB instance can experience a significant performance impact during and after converting to a Multi-AZ deployment. The impact is greater on DB instances with large amounts of storage and write-intensive workloads. We don't recommend this conversion on a production DB instance.

RDS for Db2 and IBM Db2 LUW as a target for AWS DMS

Target endpoints for data migration using AWS DMS. 

IBM Db2 LUW versions 11.1 and 11.5 

Integrating an Amazon RDS for Db2 DB instance with Amazon S3

https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/db2-s3-integration.html

Target data providers for DMS Schema Conversion

SCT tool doesn't support schema conversion into DB2 

https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Introduction.Targets.html#CHAP_Introduction.Targets.SchemaConversion

Limitations and recommendations for using native restore

• Amazon RDS only supports offline and online backups for native restore. Amazon RDS doesn't support incremental or Delta backups.

• You can't restore from an Amazon S3 bucket in an AWS Region that is different from the Region where your RDS for Db2 DB instance is located.

• You can't restore a database if your RDS for Db2 DB instance already contains a database.

• Amazon S3 limits the size of files that are uploaded to an Amazon S3 bucket to 5 TB

• Amazon RDS doesn't support non-fenced external routines, incremental restores, or Delta restores.

• You can't restore from an encrypted source database

To restore your Db2 database to your RDS for Db2 DB instance .

(Optional) To make sure your database is configured with the optimal settings for the restore operation, you can call rdsadmin.show_configuration to check the values for RESTORE_DATABASE_PARALLELISM and RESTORE_DATABASE_NUM_BUFFERS. Call rdsadmin.set_configuration to change these values, as needed. Explicitly setting these values can improve the performance when restoring databases with large volumes of data.

Limitations when using Db2 LUW as a target for AWS DMS

These limitations can affect the planning, execution, and management of your database migrations. Here are some key limitations to be aware of:

AWS DMS only supports Db2 LUW as a target when the source is either Db2 LUW or Db2 for z/OS. 

1. Supported Data Types:

   • Not all Db2 LUW data types are fully supported by AWS DMS. Some complex data types may not be migrated correctly or might need manual intervention.

   • Using Db2 LUW as a target doesn't support replications with full LOB mode. 

   • AWS DMS truncates BLOB fields with values corresponding to the double quote character ("). This is a limitation of the IBM dbload utility. 

   • Using Db2 LUW as a target doesn't support the XML datatype in the full load phase. This is a limitation of the IBM dbload utility. For more information, see The dbload utility 

   • AWS DMS doesn't support the BOOLEAN data type in your source Db2 LUW database. 

   • When the task setting Include LOB columns in replication isn't enabled, any table that has LOB columns is suspended during ongoing replication.

   • For example, certain binary types, XML types, and other complex structured data might face issues.

2. Limited Transformation Capabilities:

   • AWS DMS provides basic data transformation capabilities, but it might not support all the complex transformations required for Db2 LUW. Complex transformations may need to be handled outside of DMS, either before migration or through post-migration processing.

3. Performance Considerations:

   • Performance during migration can be affected by network latency, source and target database configurations, and the size of the dataset.

   • Db2 LUW performance tuning may be required to handle the load during migration.

4. Schema and Object Support:

   • AWS DMS may not fully support all Db2 LUW schema objects such as triggers, stored procedures, and certain constraints. Manual intervention may be necessary to migrate these objects.

   • Some specific Db2 features, such as certain types of indexes or user-defined functions, might need to be recreated manually.

5. Data Consistency:

   • Ensuring data consistency during migration can be challenging, especially for large datasets or databases with high transactional activity.

   • AWS DMS uses logical replication which might require careful planning to ensure that all data changes are captured and applied correctly.

6. Change Data Capture (CDC) Limitations:

   • There might be limitations on the types of changes that can be captured and replicated in real-time, especially with more complex or custom configurations in Db2 LUW.

   • Latency in CDC can also be a concern, requiring careful monitoring and tuning.

7. Unsupported Features:

   • Certain Db2 LUW features might not be supported by AWS DMS, necessitating workarounds or alternative migration strategies.

   • For example, advanced security features, encryption, and specific Db2 LUW optimizations might need to be reconfigured manually after migration.

8. Compatibility and Version Issues:

   • Ensure that the Db2 LUW version is compatible with the AWS DMS version you are using. Certain newer features in Db2 LUW may not be supported by older DMS versions.

   • Regular updates and compatibility checks are necessary to avoid issues arising from version mismatches.

9. Custom Configurations and Extensions:

   • Custom configurations, extensions, or third-party tools integrated with Db2 LUW might require special handling during migration.

   • Manual steps might be necessary to ensure that all custom settings are correctly replicated in the target environment.

10. Monitoring and Troubleshooting:

    • AWS DMS provides monitoring capabilities, but diagnosing and troubleshooting migration issues may require in-depth knowledge of both AWS DMS and Db2 LUW.

    • Detailed logging and analysis may be necessary to resolve complex migration issues.

Referance  : https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Target.DB2.html