Hello Michael,
What are you going to do with the 'active' archives? Migrate them to Exchange? Keep them available to users?
As for deleting in bulk. It is possible to do it via SQL, but be advised that deleting archives will hammer SQL, Index- and Storage locations. As you use Centera, are you using hardware retention? If the last = yes, what is the retention. Keep in mind that if an item has not passed retention, it cannot be deleted. I strongly recommend not deleting 1000's of archives, as that will kill your EV.
I am in kind of the same boat. We're migrating archives for active users to Exchange. When all archives which can be migrated are migrated, we will shutdown EV. Then we use the BEEP system to see if we missed someone. (BEEP = user calls service desk to ask why his archive is not reachable). We have over 160000 user archives, of which 107000 could be deleted.
Check THIS forumpost. it has the SQL query described.
Note that this line SET ArchivingState = 4
WHERE ArchivingStating = 1
needs to be changed to SET ArchiveStatus = 4
WHERE ArchiveStatus = 1
Make 200% sure you are targeting the correct archive(s). If you make an error, revert the values. (i.e. set AS = 1 where AS = 4)