Replication

In biology, replication is the act or ability to make a copy. (Mostly commonly meaning molecular replication).

• Self-replication is the act of a molecule (or any other pattern) making a copy of itself.
• DNA replication is the act of copying the genetic material of a cell (DNA) to a daughter cell is almost, but not quite, a form of self-replication because it requires the cellular apparatus to perform that replication.
• Semiconservative replication is the particular mechanism of DNA replication, of several mechanisms that were originally hypothesised, that was found to be actually used in cells.

In computer science, replication is the provision of redundant resources (software or hardware components) to improve reliability and fault-tolerance. Dynamic replication of data can also be used to improve performance. (See US Patent # 4432057). This is especially true in a multiplicity of computer systems (multiprocessors). Storage or backup of the same data on multiple file systems is an example for replication. Database replication is implemented, for example in MySQL, usually with a master slave relationship between the original and the copy. Updates are logged at the master and rippled through to the slave. The slave outputs a message stating the last update it successfully received, so that subsequent updates can be sent (and resent) until successfully applied. See also Coda and RAID.

Another example of using replication one may find in distributed shared memory systems, where it may happened that many nodes of the system share the same page of the memory - which usually means, that each node have separate copy (replica) of this page.

In statistics replication refers to repeated measurement of a phenomenon, so that the variability can be estimated.

In science, this is a synonym for Reproducibility.