Steps to restart an Interrupted Database Restore in SQL Server
There may scenario when you are restoring VLDB database backup and the restore database command interrupted due network failure, power failure, SQL Server Service restart or cluster failover. In this kind of scenario you can easily start the interrupted restore from the point of failure using WITH RESTART command.
Before you start restoring the database using WITH RESTART option check database is in Restoring State not in any other state.
You can check the database state either from SSMS object explorer or by executing below T-SQL command
select name,state_desc from sys.databases
Once confirmed that database is in restoring state execute the backup command WITH RESTART clause
RESTORE DATABASE [AdventureWorks] FROM DISK ='D:\Backup\AdventureWorks.bak' WITH RESTART, STATS = 20 GO