Monday, 28 March 2016

Optimistic concurrency control protocols in real-time database

Optimistic concurrency control protocols in real-time database, real-time database variants of optimistic concurrency control (OCC) protocols, OCC-Broadcast Commit, OCC-Sacrifice, OCC-Wait, and Wait-50 protocols


Optimistic Concurrency Control Protocols


They follow a concept called validation (or certification) of transactions’ operations. This validation is done at the end of the transaction. As the name suggests, these protocols do not prevent any transactions from accessing any data items they require. The idea is to check all the necessary formalities at the end of the transaction before commit.
In optimistic concurrency control, any numbers of concurrent transactions are permitted (even some of the transactions work on same data items). The conflict of transactions, i.e., read-write, write-write on same data items, is validated at the end of the transaction. If any conflict is found during validation, the victims are chosen and rolled back. This avoids the unnecessary blocking of resources.
The following are the variants of OCC protocol where the classical OCC algorithm is slightly changed to accommodate real-time database environments;


  • OCC – Wait
  • Wait – 50



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