About using DLO to back up Outlook PST files incrementally

DLO is configured to back up PST files incrementally by default. Incremental backup of PST files is controlled by the administrator in the Profile, or by the desktop user in Options dialog if the desktop user has been granted sufficient rights.


Outlook must be the default mail application to perform incremental backups of Outlook PST files.

The following should be considered when backing up PST files incrementally:

If you do not intend to use Outlook as your default mail application, you can disable the warning message about incremental backups.

See Setting customized options on the Desktop Agent.

When an Outlook PST file is included in a DLO backup selection, it will appear in the Desktop Agent pending queue whenever the PST file is closed. Because PSTs are a shared resource, opening and closing of PST files is controlled by a process called MAPI. Both DLO and Outlook access PSTs via the MAPI process. MAPI opens a PST upon request from the application.

Depending on the version of MAPI that is in use, MAPI may or may not close a PST in response to the following:

When the PST is closed DLO does one of the following. If the PST is being handled incrementally via MAPI (see section on incremental PSTs) DLO determines if the PST has been backed up in its entirety. If it has already been backed up then the entry is simply removed from the Desktop Agent pending queue because DLO knows the PST is in sync. If the PST is not being handled incrementally, the PST will be backed up in its entirety at this time.

See About restoring Microsoft Outlook Personal Folder files.