Dell Unity: Replication session failed with an error message: Failed: The system encountered a REST connection failure

Replication connection failed with error:

Failed: The system encountered a REST connection failure. (Error Code:0x102)
Rollback Result: Task was rolled back and marked as failed. This is because some tasks failed or SP rebooted during task execution. (Error Code:0x100a

Replication session showing error:

The system encountered an unexpected error. Try again and if that attempt fails then search for the error code on the support website or product forums, or contact your service provider, if available. (Error Code:0x6000003)

The storage array's admin credential changed.

Authentication fails between source and storage array.

1. Update the Admin credential at source and destination array in replication connection.
2. Perform "verify and update" for replication connection at both sides, It should be green.

Must verify the logs /EMC/CEM/log/cemtracer_dataprotection.log and check the instances for Authentication and Connection refused.

14:28:28 root@(none) spa:/EMC/CEM/log> less cemtracer_dataprotection.log
14 Feb 2019 05:04:15 - [RESTClient] INFO - {1:7895416:180358237}[12690|6701|dafffb40][updateConnectionStatus @ ../../../components/RESTClient/src/RESTSession.cpp:1194] We're not logged in, ip: XX.XX.XX.XX, errCode: 259
14 Feb 2019 05:04:18 - [RESTClient] INFO - {0:7895418:818009374}[12690|6701|dafffb40][updateConnectionStatus @ ../../../components/RESTClient/src/RESTSession.cpp:1194] We're not logged in, ip: XX.XXX.XX.XX, errCode: 260
14 Feb 2019 05:04:18 - [RESTClient] ERROR - {0:7895418:977739968}[12690|6701|dafffb40][handleError @ ../../../components/RESTClient/src/RESTSession.cpp:1080] AUTHENTICATION FAILED for : login request
14 Feb 2019 05:04:18 - [RESTClient] INFO - {0:7895418:977805358}[12690|6701|dafffb40][updateConnectionStatus @

14:24:19 root@(none) spa:/EMC/CEM/log> less cemtracer_dataprotection.log
mponents/RESTClient/src/HttpWrapper.cpp:305] Caught curlpp::LibcurlRuntimeError exception: Failed to connect to localhost port 8080: Connection refused, code: 7
15 Mar 2018 15:46:26 - [RESTClient] ERROR - {0:4610:454059462}[25612|25732|f1bffb40][isLoggedIn @ /builds/storage/KH/upc-Unity.17/infrastructureproviders/components/RESTClient/src/RESTSession.cpp:993] Failed to check login RESTSession: /builds/storage/KH/upc-Unity.17/infrastructureproviders/components/RESTClient/src/HttpWrapper.cpp:305 code: 258, message: Failed to connect to localhost port 8080: Connection refused, ip: localhost