| 摘要 |
A backup program for a computer system with a hard disk maintains a record o f changes made to the data in a file being backed up. During backup both the original and update file portions or records are stored, and the backup program reads the original data while other applications read the updated data. To identify whether a read operation is initiated by the backup program or by another application, the system determines, using the stack, the source of the read request. Alternatively it interrogates the user, process or task id. Access to the file by the backup program is guaranteed by manipulating the System File Table. It is ensured that the file is in a "good" state by delaying the start of the backup operation for a predetermined period. |
