Microsoft SDK for Java

Split Distribution Units

The dubuild utility can also create split, or delta, DUs. This functionality is useful for updated versions of software where some of the files in the original DU have been modified (a service pack, for example).

In order to build a split DU, you must specify a new (version 2) cabinet file, the original path, and the original DU. Whole packages that contain changed files end up in the new DU. If there are no unchanged packages, everything ends up in the new DU. This command creates its own cab file, named ~NEWCAB.cab, which holds the unchanged packages. The OSD in NEWCAB.cab does not have a reference to the original .cab file. A command line to build a split DU follows:

C:\..\>dubuild newcab.cab . /P oldcab.cab /M /I *.class

When Internet Explorer encounters a split DU in the useslibrarycodebase parameter, it follows the same steps previously described, with an additional step. If the newer version of the split DU is not present on the local system, it will be downloaded, and the OSD manifest is examined. If the earlier version of the software, pointed to by the OSD file, does not also exist on the local system, it is downloaded as well. However, if the earlier version of the split DU is already present on the system, no further action is performed.

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