Taking Differential Backups

Hi guys,

I have a question about taking differential backups; does SSMS needs access to the actual full backup .bak file in order to perform a full differential backup?

No, not for taking the backup. The information is in the system tables.

To restore using the differential backup, you will of course, need the last full backup.

No. Extent maps within the db "tell" SQL which extents have changed so that it can do the differential backup. The last full backup is irrelevant to that process.

ok great, phew.... thanks guys!!

Beware if something/somebody else takes a FULL backup then your Differential backup will be based on THAT OTHER Full backup ... this can be a problem when you come to Restore if you do not have access to the Full backup that preceded the Differential.

We've just had a situation where a Client's outsourced IT support company changed and they "well meaning" (Ha!Ha!) implemented a daily Full and Log backup which broke our Differential and TLog backup chains :frowning: