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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 ...
Mean time between failures (MTBF) describes the expected time between two failures for a repairable system. For example, three identical systems starting to function properly at time 0 are working until all of them fail. The first system fails after 100 hours, the second after 120 hours and the third after 130 hours.
This varies according to checkpoint algorithm. If all dirty pages are flushed while creating the checkpoint (as in PostgreSQL), it might contain: redoLSN: This is a reference to the first log record that corresponds to a dirty page. i.e. the first update that wasn't flushed at checkpoint time. This is where redo must begin on recovery.
PostgreSQL supports a binary communication protocol that allows applications to connect to the database server. The protocol is versioned (currently 3.0, as of PostgreSQL 7.4) and has a detailed specification. [47] The official client implementation of this communication protocol is a C API, libpq. [48]
PL/pgSQL (Procedural Language/PostgreSQL) is a procedural programming language supported by the PostgreSQL ORDBMS. It closely resembles Oracle 's PL/SQL language. Implemented by Jan Wieck, PL/pgSQL first appeared with PostgreSQL 6.4, released on October 30, 1998. [ 1 ]
PostgreSQL and some other databases have support for foreign schemas, which is the ability to import schemas from other servers as defined in ISO/IEC 9075-9 (published as part of SQL:2008). This appears like any other schema in the database according to the SQL specification while accessing data stored either in a different database or a ...
In service level agreements, it is common to mention a percentage value (per month or per year) that is calculated by dividing the sum of all downtimes timespans by the total time of a reference time span (e.g. a month). 0% downtime means that the server was available all the time. For Internet servers downtimes above 1% per year or worse can ...
In 2005 Poul-Henning Kamp, the manager of the only Danish Stratum 1 NTP server available to the general public, observed a huge rise in traffic and discovered that between 75 and 90% was originating with D-Link's router products. Stratum 1 NTP servers receive their time signal from an accurate external source, such as a GPS receiver, radio ...