# Limitations and considerations

When using IBM DB2 for LUW as a target, the following limitations currently apply.

* Clustered databases are not supported

  Information note

  You can define a separate IBM DB2 for LUW target endpoint for each of the databases in the cluster.

* To improve CDC efficiency, consider enabling the Apply changes using SQL MERGE option. For more information on this option, see [Miscellaneous tuning](https://help.qlik.com/en-US/replicate/May2026/Content/Global_Common/Content/SharedEMReplicate/Customize%20Tasks/tasks_applychangtunestab.htm#Miscella).

  Information noteWhen using Apply changes using SQL MERGE, LOBs are limited to 15 KB. If the Limit LOB Size to field is set to a higher value, errors will occur.

* When Limit LOB Size to is set, BLOBs are limited to 15 KB. If the Limit LOB Size to field is set to a higher value and a table contains BLOBs, an error will occur when the task starts.