SQL Server做完整备份步骤
四个步骤：
1. Checkpoint database means that SQL Server writes all dirty pages (pages that have changed since loaded into memory) to disk to ensure only committed transactions included in full backup.
2. Mark beginning of transaction log to validate backup file(s) whether it could be used in restore process.
3. Read data file and write into backup device.
4. Mark end of transaction log when full backup has finished.
