As I explained in a previous blog post , sometimes MVCC is not sufficient and an operation needs to block out all other concurrent modifications. NuoDB is able to lock three types of lockable resources: tables, schemas, and sequences. A resource can either be locked in SHARED mode (which still allows record modification, but no metadata modification) or EXCLUSIVE which prevents any concurrent modification.

EXCLUSIVE access is required for DDL that visits all records (various index operations for

Let us imagine a scenario that needs to prevent MVCC write skews...

One transaction increases the salary of everyone in a department by 10%; another transaction inserts a new employee with a salary X. Since the two transactions do not conflict, MVCC does not prevent either of them from committing. After both resolve, the overall salary in the department could be above the budget. To prevent a similar situation, the application developer might want to have exclusive access to the table.

NuoDB 3.2.2 exposes a new type of lock that guarantees exclusive access to a resource

Traditionally, relational databases were designed for scale-up architectures. Supporting more clients or higher throughput required an upgrade to a larger server. Until recently, this meant that implementing a read & write scale-out architecture either required a NoSQL database and abandoning traditional relational database benefits, or relying on sharding and explicit replication. There were no solutions that could scale-out and still provide complete ACID (Atomicity, Consistency, Isolation, and Durability) -compliant semantics. This tension is what inspired the NewSQL

NuoDB Administrative Improvements

There’s a new Sheriff coming to town…

In the days of covered wagons and the open trail, the small towns in the west (you know the ones) with a single dirt main street lined on each side with storefronts, wooden boardwalks and horses tied to a rail, … they all had one thing in common -- a Sheriff in charge. And if there was anything important going on, or a decision was to be made, it involved the Sheriff.

In NuoDB , a distributed SQL database that runs