What can happen?

• Client or Server crashes (HW/SW)
• Network failure
• Transaction rollback
• Transaction deadlock
• Disk problem
• Application program problem

• Tandem Computers
• Oracle's Rollback Segment
• Backup copies in "remote" location
• Checkpoints
• Transaction logs -- log files -- on separate devices?
• Recovery via "recover and roll forward" -- want redo log on a remote device (possible with Internet).
• Recovery via rollback -- when a "bad" tranaction is identified.  Undo log must have state of DB prior to each transaction.
• "Hot" vs "cold" backups.

• Physical security for computers
• Account security to validate users
create user Mo password oM;
• Access security to protect database objects (access priviledges)
grant insert on Customer to johnsomo;
grant role Clerk to Jo;
• OS security for database & file protection
Unix is notoriously insecure.  Oracle8 adds security capabilities.

audit select on TimeCard;
audit all on PurchaseOrder;
noaudit select on Movie;

Organization may be:

• Unfragmented
• Horizontally fragmented
• size=+1>Vertically fragmented
• Replicated