Netezza Equivalent to T-SQL ROWVERSION or PL/SQL ORA_ROWSCN
I'm not sure about the ROWVERSION behaviour, but ORA_ROWSCN I believe would still change if you were to update a row with completely identical values. In other words, the row contents would remain the same but its SCN would be different. 

The only practically reliable way to detect the actual change in column values would be to calculate the row checksum or hash. 

To answer your question though, consider using the createxid special column in Netezza: http://pic.dhe.ibm.com/infocenter/ntz/v7r0m3/topic/com.ibm.nz.dbu.doc/r_dbuser_data_types_ntz_internal.html

And again, a changed createxid value would not necessarily mean that any column values have changed.