Which table data triggers when we do changes to the Attachment Tab : add or delete attachments.

Question 1

Which table data triggers when we do changes to the Attachment Tab : add or delete attachments. Because I am unable to perform any custom actions on Attachments Tab with respect to changes on Items attributes.

Question 2

Where can I get the Meta data Table information.

When I add an Attachment to an Item, I can get the attachment information through Web services only after the Item Save.

So initially, when i add that attachment where is that data stored, is it in OCPLM or do we have a Meta table that stores this unsaved attachment data.