By reviewing the [official documentation](https://www.ibm.com/support/knowledgecenter/SS5FPD_1.0.0/com.ibm.ips.doc/postgresql/dbuser/c_dbuser_database_maximums.html), I could see that Record Size Limit 65,535 bytes. is defined by the Netezza database. Therefore, the [error](https://www.ibm.com/support/pages/node/462219) you are experiencing is thrown by Netezza when the total record size in a table exceeds the limit. Denodo does not impose record size limit, the maximum data length is considered as per the source type properties of each column defined during base view creation. Hence, I would suggest you to execute the delegated SQL sentence in the Netezza i.e the query which has the union all of the two tables selected in a with clause, make sure you don't add any **limit** rows in the query and check if the same error is returned in Netezza. If so, then I would suggest you to check the columns contributing to this error in the corresponding tables of Netezza database.
To obtain the SQL sentence, execute the view, then click on **"Execution Trace"** and select the bottom node. Then, go the right section and you will be able to see the SQL sentence that Denodo is executing at the Data Source.
For more information, please refer to the section [Execution Trace of a Statement](https://community.denodo.com/docs/html/browse/8.0/vdp/administration/creating_derived_views/querying_views/execution_trace_of_a_statement#execution-trace-of-a-statement) of Virtual DataPort Administration Guide.
Hope this helps!