Locks and concurrency

IBM® Netezza® SQL does not use conventional locking to enforce consistency among concurrently running transactions. Instead, it automatically uses a combination of the following mechanisms. There is no need for user intervention, commands, or hints.

Multiversioning

Each transaction sees a consistent state that is isolated from other transactions that are not committed. Because of the Netezza architecture, the hardware can quickly provide the correct view to each transaction.

Serialization dependency checking

Concurrent executions that are not serializable are not allowed. If two concurrent transactions attempt to modify the same data, the system automatically rolls back the latest transaction. This form is a form of optimistic concurrency control that is suitable for low-conflict environments.