switchover failed showing ora-12514 while using dgbroker

we are trying to do swithcover , which failed with ORA-12514 error,

it was connecting a different service name rather than the usual as shown in the alert log,

Fatal NI connect error 12514, connecting to:

(DESCRIPTION=(enable=broken)(SDU=32678)(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=IPaddess)(PORT=6189)))(CONNECT_DATA=(SERVICE_NAME=db_unique_name_DGB.sbj_bancs)(INSTANCE_NAME=sid)(CID=(PROGRAM

=oracle)(HOST=hostname)(USER=oracle))))

  VERSION INFORMATION:

        TNS for HPUX: Version 11.2.0.4.0 - Production

        TCP/IP NT Protocol Adapter for HPUX: Version 11.2.0.4.0 - Production

  Time: 13-FEB-2016 20:24:49

  Tracing not turned on.

  Tns error struct:

    ns main err code: 12564

TNS-12564: TNS:connection refused