As long as a civilization has a stable monetary system and stable institutions the scheme described here would seem to provide long term access to big data. At least two other sorts of plans have worked in absence of the above:
I do not propose hiring many stone masons to engrave our data. I imagine that the commercial CD produced from masters is fairly durable, especially if ensconced in some low tech inexpensive container. The low incremental cost affords wide-spread distribution. It is hard to be confident in this however. Unprotected amber has preserved microscopic 3D details very well for 107 years. We are beginning to decode DNA from 104 years ago and some hope to resurrect 107 year old DNA.
I see no hope of transferring large amounts of data to non-technical future civilizations. A CD would presumably arouse interest and a simple microscope would discover data thereon. A hierarchy of two or three technologies might well explain to future people how DNA or other molecular data storage held information.
I recently heard by word of mouth of a disk made by the Long Now Foundation that has writing on it spiraling inward with gradually smaller type.
Here is another technology aiming for even longer life.