To delete an SDLC port, redefine the port's protocol support to a protocol other than SDLC:
CLI> define wan port protocolSupport
Redefining the WAN port removes the SDLC port entries from the SDLC port configuration table, the SDLC link station configuration table, and the switched link configuration table associated with that WAN port. Operational table entries will remain in effect until the unit is reset. To release the port from SDLC protocol support, you must reset the unit:
CLI> reset system current reset