Release Notes

|5.24 Potential Problem When Restoring Files

|Problem: When different versions of the same file are |linked to a database at different times, the Data Links File Manager (DLFM) |Retrieve daemon does not retrieve the correct version of the file from an |archive when the database gets restored.

|Background: When a database is restored from a backup |image, the files that were linked in that backup image also get restored in |the Data Links Manager file system (DLFS) from the archive. Here is how |the Data Links Manager retrieve-and-restore process works. |

• |If the last modification time and size attributes of the current version |of a file on disk are different from the attributes of the file to |be restored from the archive, then the current file on disk is treated as a |different version of the file. The current file on disk gets saved as |filename.MOD, and the original version of the file from the |DLFM archive gets restored. For example, if the current file name is |abc, then abc gets copied to abc.MOD.
• |If the last modification time and size attributes of the current file on |disk are the same as those of the file to be restored from the |archive, then the Data Links Retrieve daemon assumes that the file has not |been modified, and it will not restore the version of the file from the |archive. |

|Important: It is possible to modify a file but not have |the last modification time and size attributes change. Such "hidden |modifications" are done by making a change that does not affect the file size, |and then resetting the last modification time attribute to that of the |original file.

|Example: Suppose you have a database called DBTEST, and it |contains a table with a DATALINK column. You then perform the following |tasks, in the order listed: |

1. |Create a file called fileA in a DLFS-mounted volume. |This is the first version of the file.
2. |Insert the fileA reference (a URL) into the DBTEST database.
3. |Take a backup of the DBTEST database.
4. |Delete the fileA reference from the DBTEST database.
5. |Delete fileA from the DLFS-mounted volume.
6. |Create another file named fileA in the DLFS-mounted |volume. This is the second version of the file.
7. |Insert the fileA reference (a URL) into the DBTEST database.
8. |Restore the DBTEST database from the backup image. |

|The DLFM Retrieve Daemon copies the second version of fileA to |fileA.MOD, then copies the first version of fileA |from the archive onto the DLFS-mounted volume as the working version of |fileA.

|However, if both versions of fileA have the same last |modification time and size attributes, the DLFM Retrieve Daemon does nothing, |because it assumes that the files are actually the same version.

|The result is that the second version of the file -- rather than the first |version -- remains on the DLFS-mounted volume. You have not truly |restored the file system to the same state it was at the time of the |backup.

|Solution: Ensure that your application does not replace a |file with a newer version of that file with the same attributes (last |modification time and size).