Do you want to compare DB2 Linux/Unix/Windows databases, structures, contents or configurations. Or do you want to compare table data or structures with DB2 for z/OS? Here’s list of products which could be useful:

• Embarcadero DB Change Manager:
  Does not support DB2 for z/OS, but great for comparing DB2 UDB’s, compares even structures and database configurations.
  http://www.embarcadero.com/products/db-change-manager
  
• DbVisualizer:
  Supports DB2 UDB’s and DB2 z/OS. Graphical tool, inappropriate for large amount of data, great for comparison of low volumes or SQL statements.
  http://www.dbvis.com/
  
  
• Altova DataSpy:
  Generally supports DB2 UDB and DB2 z/OS. Structural comparisons supported, but data comparison did not work (problem skipping differences in indexes and/or primary keys).
  http://www.altova.com/databasespy/database-compare-tool.html
  
  
• SQLManager Data Comparer:
  Not available for DB2, but for other popular database systems.
  http://www.sqlmanager.net/de/products
  
  
• AQT Advanced Query Tool:
  Works, but objects have to be compared individually, one by one. Old-fashioned end-user front-end. Advanced edition required.
  http://www.querytool.com/features.html#compare
  
  
• SQL Maestro Data Sync:
  Up-to-date front-end, available for all major database systems. Works for DB2 UDB, but does not support DB2 for z/OS.
  http://www.sqlmaestro.com/de/products/db2/datasync/
  
  
• SQL Edit DTM Data Comparer:
  Product supports DB2 for Linux/Unix/Windows and DB2 for z/OS. Its possible to select objects by schema name. Presentation of comparison results is a bit old-fashioned. Compare reports not suitable for large amount of tables and/or data.
  http://www.sqledit.com/dcmp/index.html
  

Diverse:

• http://www.dbsolo.com
• http://www.dbbalance.com/products.htm
• https://www.red-gate.com/products/

If you know other useful tools, please send me an email.