The [DELETE_ITEM_COMPLIANCE (0x8)] reason code means that your storage device has a hardware-enforced retention on the item which is not satisfied, and therefore the storage device is disallowing the deletion. This commonly happens with EMC Centera devices, though they're not the only ones with functionality that falls under this code.
Check with the storage vendor to see if there is any way to alter this hardware-based retention.
This question is a little hard to understand, but let's give it a shot.
When it is archived, a single item is split into one saveset and 0 or more SIS parts. The exact number of SIS parts depends on various characteristics of the item, which we don't need to get into here. The important thing to understand is that
(saveset + SIS parts) = item
The Centera device doesn't give a hoot about savesets or SIS parts. It is all about Clips (containers) and Blobs (data objects, loosely analogous to files). When collections are enabled on a Centera partition, then EV stores the savesets and SIS parts from multiple items together as Blobs in a single Clip. So a Clip will contain some combination of saveset and SIS part data; they might be from different items, even different archives, but what ties them together is they were all archived about the same time, so they end up in the same Clip on the Centera. When EV needs to retrieve a specific saveset or SIS part from a Clip, it provides the Centera with the ClipId and a data offset for the Blob representing the data it needs.
It is possible to get a list of all SavesetIds for a single archive. You would use a SQL query like this against the Vault Store database that contains the user's archive:
SELECT dbo.CombineSavesetId(IdChecksumHigh, IdChecksumLow, IdDateTime, IdUniqueNo, IdTransaction) AS SavesetId FROM Saveset JOIN ArchivePoint ON ArchivePoint.ArchivePointIdentity = Saveset.ArchivePointIdentity WHERE ArchivePoint.ArchivePointId = 'ArchiveIdGoesHere'
If what you meant was rather to get a list of all Centera ClipIds, well that's also possible, like this:
SELECT DISTINCT Collection.RelativeFileName AS ClipId FROM Saveset JOIN ArchivePoint ON ArchivePoint.ArchivePointIdentity = Saveset.ArchivePointIdentity JOIN Collection ON Collection.CollectionIdentity = Saveset.CollectionIdentity WHERE ArchivePoint.ArchivePointId = 'ArchiveIdGoesHere'
Finally, if an archive is successfully delete then yes, the records of its items will be removed from EV's Saveset table in the Vault Store database. However, a record of each deletion, including the SavesetId of the item that was deleted, is kept for thirty-two days in the JournalDelete table. So if you need to know the SavesetId of an item that was deleted, you can find it if you look quickly enough.
I hope that helps!