Configuring the external database limit provides the upper limit for the number of non-default AS-external-LSAs in a router's link-state database. The router enters overflow state when it reaches the limit. The router does not hold more than the configured non-default AS-external-LSAs in its database.
You must set the LSDB limit identically in all routers that are attached to the OSPFv3 backbone or any regular OSPFv3 area (for example, OSPFv3 stub areas and NSSAs are excluded).