can rman backup a subset of a table
RMAN only works at the block level &amp; has no idea about the contents of a given block, and therefore cannot do this.

You need to use expdp with the query parameter:

expdp phil/phil directory=myexportdir dumpfile=yourtable.dmp query=yourtable:\"where groupid in (1,2,3)\" tables=yourtable


Obviously, this isn't incremental. There's no really easy way of doing it incrementally based on a query/the data. You'd have to roll your own tool to do it - flashback query could help.

What data volume are you dealing with? If &lt; a few million rows, just export the full data each time.