Backup operation fails, Failed to connect to backup agent: Unable to perform request (101). (4215650)

Error Text: All operations failed.
Warning : Failed to connect to backup agent: Unable to perform request (101). The target computer is busy processing requests started on the computer 'XXXX'. Please try again later.

A previously scheduled backup is still running when the new one tries to start.

1. Ensure that more than one scheduled backup is not trying to run at the same time. Verify within the scheduled tasks in Windows
2. Ensure that running backups are not still running when the next scheduled backup for that DC starts
3. If the domain controller has the preinstalled backup agent, try restarting the Quest Backup Agent service on the DC
4. The backup agent could also be in a hung state, bring up the task manager on the DC and end the erdagent or backupagent64 task and retry the backup
5. Reboot both the RMAD server and the DC.
6. Ensure the credentials to access the backup agent on target DCs are the correct ones.
7. Make sure that the appropriate windows firewall inbound rules are created in the target DC if the backup agent was installed manually. If the rules do not exist, you may create them manually or reinstall the backup agent selecting the option to create firewall rules to allow the install wizard to create the rules required to allow traffic on default port TCP 3843 and the RPC / EPMAP rule.

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