[hvindin]

Buy the concept of taking data offline or to another network applies to this.

For example, while banks are required to keep tons of data for legal reason, the ones I've worked with have procedures where, for example, tellers are required to shred everything and send it for incineration. Then, the digital copies, once they can only be required if theres legal compulsion going on (ie after x number of years), are transfered by batch jobs which encrypt everything with a key generated by a CA that is offline most of the time, to a tape library which is only online for batch writes and can only be brought online manually by physically going into the data center. Then, after a little more time, but still within legally required reporting periods, the tapes are moved into a warehouse which very much resembles a bank vault.

And as soon as theres a reason that the data isnt mandatorily kept, the tapes are destroyed.

Honestly the security around those tapes is higher than bricks of cash, and they're destroyed even more readily.