Dependency patterns that are not a simple graph
You can run a recursive hierarchical query on a data set that includes complex dependencies, such as multiple root nodes, or multiple parent nodes for child nodes. However, cycling might occur and more records might be returned, based on hierarchical data tree structures.
The CONNECT BY clause cannot analyze data sets that include cycles where some child nodes are identified as ancestors of their parent node. If your data set includes cycles, the cycles might be artifacts of rows that contain invalid data.
If the data set that the self-referential table describes includes more than one hierarchy, include the START WITH clause with a condition that is only true for the root of the hierarchy that you want the recursive query to return. Run a separate query on the table for each hierarchy, using a different START WITH clause to specify the root in each query.