NetWorker：NVP vProxy：MSVMAPPAGENT SQL 事务日志备份失败“MSSQL Agent failed to create a transaction log backup.”

YYYY/MM/DD HH:MM:SS INFO:   [89] MSSQL: Executed MSSQL Agent operation 'backup_transaction_log' on guest VM.
YYYY/MM/DD HH:MM:SS INFO:   [89] MSSQL: Executed MSSQL Agent operation 'monitor' on guest VM.
YYYY/MM/DD HH:MM:SS INFO:   [89] MSSQL Agent: Performing transaction log backup for SQL instance 'VM_NAME'
YYYY/MM/DD HH:MM:SS ERROR:  [89] MSSQL: MSSQL Agent: 
YYYY/MM/DD HH:MM:SS ERROR:  [89] MSSQL: backup_transaction_log: Failure monitoring progress: MSSQL Agent: 
YYYY/MM/DD HH:MM:SS ERROR:  [89] MSSQL: MSSQL Agent failed to create a transaction log backup.
YYYY/MM/DD HH:MM:SS ERROR:  [89] MSSQL: Backup of the application "MSSQL Agent" on the virtual machine "VM_NAME" has failed.
YYYY/MM/DD HH:MM:SS INFO:   [89] MSSQL: Disconnected from MSSQL Agent in "VM_NAME".

目标虚拟机的 C：\Program Files\DPSAPPS\MSVMAPPAGENT\logs\msvmagent_appbackup.log显示：

52701:msvmagent_appbackup: Command line: C:\Program Files\DPSAPPS\MSVMAPPAGENT\bin\msvmagent_appbackup.exe -i - 
37693 MM/DD/YYYY HH:MM:SS msvmagent_appbackup NSR info SQL Connection to VM_NAME is created. SQL Server Version is 13.00.5026
...
153887:msvmagent_appbackup: Microsoft SQL server documentation provides details about the following SQL Server Provider error:
38008:msvmagent_appbackup: The server principal "NT AUTHORITY\SYSTEM" is not able to access the database "SQL_DB1" under the current security context.
153416:msvmagent_appbackup: (Error: 916)
37938:msvmagent_appbackup: Failed to obtain filegroups for SQL_DB1.
Backing up SQL_DB1...
172257:msvmagent_appbackup: Backup of SQL_DB1 failed.

MSVMAPPAGENT 在 SYSTEM 帐户下运行，用于数据保护操作。  配置虚拟机中的所有 SQL Server 实例以授予“NT AUTHORITY\SYSTEM”帐户 sysadmin 权限：