Shared caching is a new feature of SSIS 2012 that could improve performance when using the same large lookup table across multiple packages. It could be replicated by saving to a raw file in SSIS 2005/8, however this should be faster.
Prior to SSIS 2012 it was not possible to re-use or share the same cache across packages. What that meant is if you created a cache you will be able to consume it only in the very package where the cache was instantiated. Therefore, a developer could take only two routes from here – either make as much heavy ETL processing as possible inside the same package where the cache resides, or populate yet another cache object in every other package where it is needed. The latter was
especially harmful leading to unnecessary heavy extra database calls and an extended development time. This limitation has been overcome in the SSIS 2012 release.