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12.3 XST - Hierarchy separator changed for record type in 12.3 from 12.2
Designs which have a simple record type defined could see failures with their constraints in both XCF and UCF files, where in 12.2 the hierarchy separator was a ".", but now in 12.3 it is "_".
Constraints files are likely to cause failures when porting designs from 12.2 to 12.3, or 12.4.
This change was done intentionally to fix an issue in NGDBuild. Users who experience this issue should modify their constraints to use the "_" instead of the "." for their hierarchy separator.