About Spare Cores
When a dataset is applied to a cable, all cores specified in the dataset that do not exist in the cable are created as spare cores. Spare cores are instances of catalog fibers defined in the Design Properties dialog box as a spare core. To define a fiber as a spare core, it must have the class parameter with the value set to spare.
The name of the fiber designated as a spare core appears in the Spare Core box in the Design Properties dialog box. To designate a different fiber as the spare core, click and select the required catalog fiber. If a spare core is required but has not been designated, one is created automatically.
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Spare cores can also be created when a predefined cable containing some cores without shapes are instanced. This can occur when the routed connectors have fewer ports than cable cores.