I just want to add a little to this thread since some may use an EMC Centera. A Centera essentially has two logical modes, Basic Mode (retention is setable but can be overridden, deletes are allowed regardless of application retention), and Compliance, where retention is automatically set and can't be altered. There's a third Compliance Plus which allows zero privileged deletes.
HOWEVER in EV when setting up a Vault Store partition if you select under retention for the Centera to get it's retention from EV "For All Centera Models", you will NOT be able to do a privileged delete on those items though EV. The Clips will get the retention from the EV console. For instance we had a retention of 5 years, and the Vault Store Partition was set to "For all Centera models". Now every clip we have archived can not be deleted for five years. Even though our Centera is in Basic Edition.
Essentially when you set up that Vault Store partition, if you select "For all Centera Models" you turn your 'Basic Edition Centera', into a Compliance Plus Edition Centera (EMC can delete the Clip, however through the EV application you cannot, so priveleged deletes work using the Content Address, but not through the application using the SSID).
It's very dangerous as we have had some of our Vault Store partitions created with the "for all Centera models" setting, and now we are completely unable to delete the data. IMO this is very dangerous and EV doesn't do enough to warn the user of the implications of setting this check box. Be very careful when an EMC Centera, for future reference set in the Vault Store Partition to "NEVER". If you want to use the Centera for your retention, then do it through the CLA to the Centera.