Concepts inSerializable snapshot isolation in PostgreSQL

Snapshot isolation

In databases, and transaction processing (transaction management), snapshot isolation is a guarantee that all reads made in a transaction will see a consistent snapshot of the database (in practice it reads the last committed values that existed at the time it started), and the transaction itself will successfully commit only if no updates it has made conflict with any concurrent updates made since that snapshot.  more from Wikipedia

Distributed lock manager

A distributed lock manager (DLM) provides distributed software applications with a means to synchronize their accesses to shared resources. DLMs have been used as the foundation for several successful clustered file systems, in which the machines in a cluster can use each other's storage via a unified file system, with significant advantages for performance and availability. The main performance benefit comes from solving the problem of disk cache coherency between participating computers.  more from Wikipedia

PostgreSQL

PostgreSQL, often simply Postgres, is an object-relational database management system (ORDBMS) available for many platforms including Linux, FreeBSD, Solaris, Microsoft Windows and Mac OS X. It is released under the PostgreSQL License, which is an MIT-style license, and is thus free and open source software. PostgreSQL is developed by the PostgreSQL Global Development Group, consisting of a handful of volunteers employed and supervised by companies such as Red Hat and EnterpriseDB.  more from Wikipedia

Lock (database)

A lock is used when multiple users need to access a database concurrently. This prevents data from being corrupted or invalidated when multiple users try to write to the database. Any single user can only modify those database records (that is, items in the database) to which they have applied a lock that gives them exclusive access to the record until the lock is released.  more from Wikipedia

Two-phase locking

In databases and transaction processing, two-phase locking (2PL) is a concurrency control method that guarantees serializability. It is also the name of the resulting set of database transaction schedules (histories). The protocol utilizes locks, applied by a transaction to data, which may block (interpreted as signals to stop) other transactions from accessing the same data during the transaction's life.  more from Wikipedia

Isolation (database systems)

In database systems, isolation is a property that defines how/when the changes made by one operation become visible to other concurrent operations. Isolation is one of the ACID (Atomicity, Consistency, Isolation, Durability) properties.  more from Wikipedia

Serializability

In concurrency control of databases, transaction processing (transaction management), and various transactional applications, both centralized and distributed, a transaction schedule is serializable if its outcome (e.g. , the resulting database state) is equal to the outcome of its transactions executed serially, i.e. , sequentially without overlapping in time. Transactions are normally executed concurrently (they overlap), since this is the most efficient way.  more from Wikipedia

Database transaction

A transaction comprises a unit of work performed within a database management system (or similar system) against a database, and treated in a coherent and reliable way independent of other transactions.  more from Wikipedia