Consistency

Consistency

1. ACID

   • Atomicity
   • Consistency
   • Isolation
   • Durability

2. Update Consistency

   • Update without concern in single user
   • Update the same data
   • Concurrency control for overwriting

3. Locking methods

   • Pessemistic
     • Write locks
   • Optimistic locking
     • Determines most up to date

4. Consistency model

   • Lipcon (2009)
   • Strict
     • Must return data from write
     • Same node
     • Distributed transactions
   • Eventual
     • Eventually return data
     • Inconsistent as updating

5. Versioning

   • Timestamps
   • Multi-versions
     • Timestamp for each tuple
     • Multiple versions stored.
   • Vector clocks
     • Ordering of events.