Abstract: When a network element (NE) detects a trouble in an operation system (OpS) for operating the NE itself, a representative NE is determined among a plurality of NEs operated by this OpS. The representative NE selects a substitute OpS from other OpSs and transmits a request for operating the plurality of NEs to the substitute OpS. Thereafter, the plurality of NEs come under the operation of the substitute OpS. The substitute OpS operates the plurality of NEs based on the operation request.

Abstract: When a network element (NE) detects a trouble in an operation system (OpS) for operating the NE itself, a representative NE is determined among a plurality of NEs operated by this OpS. The representative NE selects a substitute OpS from other OpSs and transmits a request for operating the plurality of NEs to the substitute OpS. Thereafter, the plurality of NEs come under the operation of the substitute OpS. The substitute OpS operates the plurality of NEs based on the operation request.

Abstract: A secondary storage device using a nonvolatile semiconductor memory in which individual block areas constituting the nonvolatile semiconductor memory can be used up to their limit of use. When the number of repetitions of erasure in a second block area has reached a predetermined reference value, a searching unit searches active block areas for an alternate block area. A second writing unit writes information which has been stored in the alternate block area, into the second block area. A second correspondence modifying unit associates the physical block number with the logical block number and causes a logical-physical correspondence storing unit to store the correspondence of the thus-associated block numbers. A second erasing unit erases the information stored in the alternate block area and treats the block area with the physical block number as a spare block area.