You can set the classification in the policy as you have explained, for example Gold.
If using SLP (storage life cycle policy) you can also set a classification here, eg, Gold
An SLP is like a STU (if set, you select an SLP in place of a STU in the policy). An SLP writes a backup as normal, but then can automaticlally run more operations, for example duplicate. So you backup to SLP, and in the 'backgroud' it goes off and makes x numbers of copies.
If you have multiple SLP with different classifications, eg gold and silver, and, if in the policy, you define it as Bronze, you will NOT see the gold or silver SLPs as available in policy storage. If you then change the policy to Gold, you will only see the Gold SLP, not the silver.
Therefore, it is a way of ensuring policies only write to certain SLPs.
You may have really important data that you mark as Gold, and multiple SLPs, some of which goto high end disk, and then make multiple copies - so this SLP would be Gold also.
You may have les important data that only writes to disk and then a single copy to tape, this might be defined as silver.
It's simply a way of ensuring certain policies only write to specific storage.
