via Autodesk – Autodesk Softimage Services & Support – Autodesk® Softimage® 2011 Service Pack 2.

The Softimage 2011 Subscription Advantage Pack version of this service pack is available from the Subscription Center.

These service packs are basically a repackaging of HotFix3 into a service pack.
From the README:

Coexistence
Softimage 2011 SP2 is a full build and can co-exist with Softimage 2011 and Softimage 2011 SP1.
Neither Softimage 2011 nor Softimage 2011 SP1 is required to be uninstalled first.

Licensing

Softimage 2011 SP2 uses the same license as Softimage 2011. When installing Softimage 2011 SP2:
– Enter the product key 590C1 and your Softimage 2011 serial number, and then click Next.
– If you have a Network license, click Configure to switch to the Network licensing method.

Documentation

Softimage 2011 SP2 includes full English and Japanese documentation

The full list of fixes is as follows:

FELX-1993: Scene Corruption and Failed Imports Using Models Containing Corrupted Materials
FELX-1991: Repair Shader corruption for previously persisted scenes
IMPORTANT: If problems still occur when working with external material libraries, change them to be internal.

Also included are the fixes that are found in HOTFIX 1 and 2 which addressed the following issues:

FELX-1702: Disconnected shaders when importing Referenced Model
FELX-1651: Scene Corruption due to Material
FELX-785: 3rd party renderers crash on Linux
FELX-670: Custom renderer DirtyList isn’t cleared properly
FELX-120: UVunfold fails to load when in suite license mode
FELX-88: Scene corruption – Softimage crashes when you try to load scene after saving it
UDEV00258435: Saved scene is corrupt