We have some queries regarding Differential backup and restore of MSSQL using its VSS writer.
During backup my application first take full backup, which backup both database and log transaction files i.e .mdf and .ldf files and during the differential backup, it backups only the changed blocks of database(.mdf file) provided by MSSQL VSS writer. There are no issues in backup.
Our application does a VSS based restore. In this, first we restore the full backup data i.e both database( .mdf) and transaction log(.ldf)files. Then it writes the differential/changed chunks to the corresponding database (.mdf) file. The VSS writer does not give any error during the actual restore process. But the databases are not accessible after restore , they are in corrupted state. The SQL Server service stops after the restore. It cannot be started. The application logs contains errors related to transaction log number mismatch due to which we can say that the database restore has actually failed.
Also after restoring the VSS partial chunks , I tried restoring SQL data by using the restore database command of SQL i.e"RESTORE Database [Database name]". But again the restore failed.
So I have a few queries here:
- Can we restore the database using only the VSS provided partial/differential data chunks?
- If the above is true then why the restore is failing while restoring the transaction logs. Am I missing some step?
- Is there some kind of recovery command needed after restoring Full backup + Partial chunk backup to get the databases in a consistent state?