What issues can arise if one of the SPEF files (or RC corner databases) is outdated, and how does that affect slack at the PnR stage?

o   Mismatch with Layout: An outdated SPEF reflects an older version of the layout. If placement or routing has changed since the SPEF was generated, the RC values in the SPEF will not accurately represent the current physical structure. Wire lengths, adjacencies (coupling capacitance), and via counts will be wrong.

o   Mismatch with Process/Library: If the RC corner data itself is outdated (e.g., from a previous PDK version or library characterization), the fundamental R-per-square or C-per-unit-length values used for extraction might be incorrect for the current process target, even if the layout is current.

For ex, if earlier net was longer and hence in old spef, RC is more. Now latest db, net is short, RC  is less but using old spef hence timing calculation will be pessimistic and vice versa.

If new net was added in DB, that will not have any extracted parasitics in spef. Hence results in in accurate delay calculation for that net.