User:Comps

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Contributions to Wikipedia since March 2006:

(unfortunately with no others' contributions to structure and content; others' edit and language contributions are appreciated)

Serializability

New term introduced for clarity:

Materialized conflict

A regular conflict graph has an edge for every materialized conflict; a regular wait-for graph has an edge for every non-materialized conflict (typically due to blocking by a lock). According to the common conventions directions of edges represent in the two graphs types opposite time orders between conflicting operations. The new term allows a unified treatment for both materialized and non-materialized conflicts, which simplifies the discussion about Commitment ordering (CO; see below).

Global serializability

Commitment ordering (CO)

New terms introduced for clarity and simplicity of presentation:

Voting deadlock

A voting deadlock in the atomic commitment protocol. In the original CO papers these deadlocks are discussed and referred to only as "deadlocks." The new name better describes them for the respective discussions and separates them from other deadlock types.

Augmented conflict graph

This graph has an edge for every conflict, either materialized or non materialized, and it is the union of the (regular) conflict graph with the (reversed edge, regular) wait-for graph. In the presence of CO this graph is a (reversed edge) wait-for graph for voting, and has a global cycle iff a voting deadlock exists. This graph allows a more compact description of the conditions for voting deadlocks, which are an essential element in the operation of the distributed CO algorithm.

The History of Commitment Ordering

Two-phase locking

Concurrency control in databases section in Concurrency control - Almost a complete rewrite and major expansion. An expanded lead section to the containing article.

Database - Major reorganization, rewrite, expansion, and multiple section addition. A revised and expanded lead section. Since 6 May, 2011

Two-phase commit protocol - Major rewrite and expansion of lead section. A new section: Implementing the two-phase commit protocol.

Schedule (computer science) - Major reorganization, lead section revision, and new opening section: Describing a schedule formally.

Index locking - A complete rewrite.

Database management system - Major revision of lead section (12 May, 2011)

in these articles:

Distributed concurrency control

Global concurrency control

Snapshot isolation