error in listener log for 2 node rac-continously writing for every 5 minutes

HI All,

Could you please give the solution for below.

Is there any impact , If not why these are frequently showing in the listener logs.

For past two days our bluk insertion job failed to insert data to Live server.

datbase version is 10.2.0.5 and 2 node rac on linux platform

error in listener log: for both nodes

Tns error struct:
    ns main err code: 12545
    TNS-12545: Connect failed because target host or object does not exist
    ns secondary err code: 12560
    nt main err code: 515
    TNS-00515: Connect failed because target host or object does not exist
    nt secondary err code: 0
    nt OS err code: 0