VoltDB

VoltDB is a NewSQL OLTP relational database that supports SQL access from within pre-compiled Java stored procedures. While direct SQL access is supported, the most efficient form of interaction is using stored procedure calls, as it involves fewer network trips. Stored procedures are written in Java by extending a class called VoltProcedure' and implementing a ‘run()’ method that includes both SQL statements and supporting Java logic. Internally data is managed by a C++ core to avoid garbage collection issues. VoltDB relies on horizontal partitioning down to the individual hardware thread to scale, k-safety (synchronous replication) to provide high availability, and a combination of continuous snapshots and command logging for durability (crash recovery). VoltDB is based on H-Store. It uses a shared-nothing architecture to scale. Data and the processing associated with it are distributed across the CPU cores within the servers composing a single VoltDB cluster. By extending its shared-nothing foundation to the per-core level, VoltDB scales with the increasing core-per-CPU counts on multi-core servers. By making stored procedures the unit of transaction and executing them at the partition containing the necessary data, it is possible to eliminate round trip messaging between SQL statements. Stored procedures are executed serially and to completion in a single thread without locking or latching, similar to the LMAX architecture. Because data is in memory and local to the partition, a stored procedure can execute in microseconds. VoltDB's stored procedure initiation scheme allows all nodes to initiate stored procedures while avoiding a single serializable global order. VoltDB is ACID compliant. Data is written to durable storage. Durability is ensured by continuous snapshots; asynchronous command logging, which creates both snapshots and a log of transactions between snapshots; and synchronous command logging, which logs transactions after the transaction completes and before it is committed to the database. This ensures that no transactions are committed that are not logged and that no transactions are lost. == History ==

H-Store H-Store was an experimental database management system (DBMS). It was designed for online transaction processing applications. H-Store was developed by a team at Brown University, Carnegie Mellon University, the Massachusetts Institute of Technology, and Yale University in 2007 by researchers Michael Stonebraker, Sam Madden, Andy Pavlo and Daniel Abadi. H-Store was promoted as a new class of parallel database management systems, called NewSQL, that provide the high-throughput and high-availability of NoSQL systems, but without giving up the transactional consistency of a traditional DBMS known as ACID (atomicity, consistency, isolation and durability). Such systems operate across multiple machines, as opposed to a single, more powerful, more expensive machine. H-Store was able to execute transaction processing with high throughput by forgoing many features of traditional relational database management systems. H-Store was designed as a parallel system to run on a cluster of shared-nothing, main memory executor nodes (processor + memory + storage). The database is partitioned into disjoint subsets each assigned to a single-threaded execution engine assigned to one core on one node. Each engine has exclusive access to all of the data in its partition. Because it is single-threaded, only one transaction at a time can access the data stored on that partition. No physical locks or latches are included in the system, and once a transaction is started, it cannot stall waiting for another transaction to complete. Throughput is increased by increasing the number of nodes in the system and reducing partition sizes. H-Store was licensed under the BSD license and GPL licenses. By 2009, the VoltDB company developed a commercial version. The final release of H-store was in 2016. VoltDB VoltDB v5.0 introduced a database monitoring and management tool, the VoltDB Management Center (VMC for short). VMC provides browser-based one-stop monitoring and configuration management of the VoltDB database, including graphs for cluster throughput and latency as well as CPU and memory usage for the current server. VoltDB version 5.1, released in March 2015, introduced database replication (DR) functionality, removing any single point of failure. DR provides simultaneous, parallel replication of multiple partitions and binary logs of transaction results, saving the replica from having to replay the transaction. V6.0 ==See also==