There can be several reasons why a node is caused to rerun, and note that it sometimes only appears to rerun. Anytime you run a flow, SAS Enterprise Miner will check the preceding nodes to see if they need to be rerun. Even if they do not, the node might show a spinning green circle while it is being checked. You can only know if a node has actually rerun if you check the timestamp next to Last Run Time in the node property sheet.
You have the ability to Create Grouping Data and can then later can Import Grouping Data by specifying the corresponding properties in the property sheet. Once the node has been run, you can also freeze the groupings. If the problem is intermittent, make sure you aren't either running into disk space issues or java memory or getting disconnected from your data source. SAS Enterprise Miner relies on views that require access to the data so losing the connection to the database keeps it from functioning as expected.
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