I contacted with VMware Support and I received this answer (as you can see process to move media is impractical, especially when you have a lot of clients and you must check all their files...):
2 Storage Clusters
Gold - Gold Storage Policy
Silver - Silver StoragePolciy
1 Catalog with storage as Gold
Task
1) Change storage policy of catalog to silver
ISO still has not changed datastore or storage policy
2)Updated ISO by adding test in the description box - No change in any of the iso's properties
3)Created new catalog called Silver using the silver storage policy
4)Moved test.iso from test cataog (gold) to copy-move catalog(silver)
The task verified in Vcenter and now test.iso shows as silver storage policy and has moved to a datastore with the silver policy
Test 2
1)Chnage the storage policy of the copy-move catalog to Gold
2)Disabled storage of a datastores that belong to silver storage policy
3)Put into maintenance mode all datastores belonging to silver storage policy in vcenter
No iso's were migrated from this datastore automatically
When updating the ISO this did not change Storage Policy
Test 3
2 datastores in Gold storage cluster
iscii has iso-test - put this datastor into maintenance mode
Update iso in vcloud, this forced a move of the iso to other datastore
Conclusion
To change the storage policy of a media file a new catalog must be created and the media file manually moved.
To change the datastore of media that belong to the same storage policy in a storage cluster, put the datastore into maintenance mode and update the iso in Vcloud. The media file will then relocate to the next available datastore in the cluster.